how do you change pointers on a macbook air

Hi.

You can't change the pointer/cursor in the latest versions of OSX.

What you can do however is to change the size of your cursor.

Choose Apple > System Preferences >Universal Access

And there you have it on the first page of Universal Access.

If you want just to change the size of the cursor -

System Preferences > Accessibility > Display and adjust the Cursor Size slider.

Can't help with changing its appearance, sorry. Perhaps someone else here can.