To make a rectangular selection or a free form selection, choose this option.

If you want to make a rectangular selection, press the mouse button at the starting point of the area to be selected, drag it towards the end point, and release. A dotted line of the selection will appear.

In case you want to make a free form selection, press the mouse button and select the area you want. As soon as you release the mouse, the selected area will appear as a rectangle. Only the pixels within the selection are selected.

If you move the mouse inside the selected area the cursor will change to mark the selection.

To cut or copy your selection, use the keyboard combination CTRL+V (copy), CRTL+X (cut), or CTRL+V (paste).
Before pasting, you have to copy or cut the selection.

If you don't want to copy the pixels with the background color of your current pallet, choose the lowest option in the option menu.

If you take a closer look at the dotted line of the selection area, you will notice slightly larger dots at the corners and middle of the selection.
Position your mouse carefully on one of these dots to stretch the selection horizontally and/or vertically (right image).
Stretching your selection will destroy your carefully placed pixels, which makes this option not very useful for creating detailed pixel art illustrations.

Use the eraser to remove pixels.
You can choose between different brush sizes.

The background color is used for the pixels you remove.
Use the left mouse button to remove all pixels; use the right mouse button to only remove pixels with the foreground color.

Use 'fill' to paint a large area with either the foreground color (left mouse button) or background color (right mouse button).

Use the eyedropper to determine a specific color. Move the eyedropper to a specific pixel and press on the left mouse button to use the color of the selected pixel as foreground color, or the right mouse button to use the color of the selected pixel as background color.

Use this option to magnify your illustration. Once selected, you will see a rectangle with a black outline (the outline doesn't affect your illustration). Position the rectangle over the area that you want to magnify and click to see it closer up, depending on the magnification you choose (1x (original size), 2x, 4x, 6x or even 8x).

Once the illustration is magnified, MS Paint automatically jumps back to the previously selected option.

I use this option a lot. I regularly draw individual pixels when zoomed in, and then review the illustration in its original size.

The illustration should look good in its original size, if it does magnified that's okay, but the original size is the one that counts.

Press the right or left mouse button to paint in the background/foreground color. The size of the pencil is one pixel, which is ideal for creating detailed pixel art illustrations.

Hold down the shift key while drawing, to draw perfectly straight horizontal or vertical lines.

Press the right or left mouse button to paint in the background/foreground color.

Instead of the pencil tool, you can use the paintbrush tool, since it has some extra features; you can choose the size and shape of the paintbrush.

Use this option to paint multiple pixels at the same time. You can choose between three airbrush sizes in the option window.
As with the pencil option, you can use the airbrush to paint with the foreground color (left mouse button) or background color (right mouse button).

Keep the left or right mouse button pressed to increase the intensity of the pixels.

You don't have much control over the placement of pixels with the airbrush tool, which makes this option not very useful if you want to create very detailed pixel art illustrations.

Click and drag the mouse to create a text field.
Choose the font you want, the size, and the style (bold, italic, and/or underlined).
The text color will be the foreground color of the pallet, the background is either the background color or transparent, depending on the selection of the background tool.

If you are happy with the text you just added, click outside the text field to paste the text into your illustration.

Use this option to draw straight lines.
Click and hold down the left mouse button to position the starting point of the line, move to the position where you line needs to end, and release the left mouse button to draw the line.

Press the right or left mouse button to draw a line in the background/foreground color.

Choose the thickness of the line in the option window.

If you press the shift key while drawing the line, the line will either be horizontal, vertical, or diagonal.

Use the 'curve' tool to draw curved lines.
First you have to define the starting point and end point of the line, just as with the line tool option. Once you have fixed the end point of the still straight line, you can click one or two times to alter the straight line, which then becomes a curve.

I never use the option to click twice to change the curve, because it's then quite difficult to control the curve. After the first change of the straight line, choose another option in the menu to bypass the second click.

Choose the thickness of the curve in the option window.

Use this option to draw a rectangle.
You can choose between three options in the option menu; the first one creates an outline in the foreground color, the second option creates an outline in the foreground color and a fill in the background color; the third options draws a rectangle in the background color without an outline.

To create a square, hold down SHIFT and use the left or right mouse button to create the square.

Just as with the rectangle drawing tool, you can choose between three options in the option menu; the first one creates a polygon in the foreground color, the second option creates an outline in the foreground color and a fill in the background color, if the starting point and end point of the polygon are the same; the third option draws a rectangle in the background color without an outline.

Hold down SHIFT to draw lines with a 45- or 90-degree angle.

Instead of drawing a rectangle, this option draws an oval.
You can choose between three options, just as with the rectangle drawing tool.

Instead of drawing a rectangle, this option draws a rectangle with rounded corners.

You can't change the size of the rounded corners.

You can choose between three options, just as with the rectangle drawing tool.