How can I make an icon?Cause I want to put all my favorit starwars characters together!!!

That is entirely dependent upon what kinds of image edited programs anda have access to. I make mine with both Paint and Microsoft Picture Manager, which are built into my computer.
Alternatively, anda could use free online image editors like lunapic.com atau photobucket.com.

Photoshop, Gimp, Photopad. Basically any foto editing software out there.