how do use the mouse pad?

llizah101 wrote:

i don't know how to use my fingers on the mouse pad.

You use a mouse on the "mouse pad" not your fingers:

If you are asking about the "track pad" see FoxFifth's post.

The following Apple Support article from the MacBook Air User Guide may help: MacBook Air trackpad - Apple Support

The mouse will do the screen work, all you need to do is move it around on the pad and either single click, double click or right click as appropriate.