You can easily select ToolTip control from Toolbox as you can see in this screenshot and we can drop it to our form.So very simple just drag and drop to use it.

After adding tool tip control, we can set the property of any control in the form. To set property of any control in the form select that particular control and change the ToolTip property as demonstrated in the image below.

Here is the example of tool tip.

Tool tip for Exit Button