Ooohhh no wonder you are so excited
You are going to have lots of fun now.
As to how to use: Start by drawing lines. Keep practicing until you can make a straight line all acorss a page that is as thin as a pencil line.
The farther away from the cake the wider the line will be; the closer you get the thinner it will be.
Always start spraying (pull the trigger) *before* you reach the edge of the paper and stop *after* the paper ends. Next get out some patterened paper towels &/or coloring book pages and just start playing trying to fill in any pictures. That's just a few points to help get you started
Make your self an enclosure by using a big cardboard box w/one side cut out OR buy one of those tri-fold display boards (you can get them even at the $ stores these days or try Michael's or Hobby Lobby). Put down lots of newspaper to help absorb overspray. YES, there *will* be overspray no matter how careful you are.
I remember reading about one gal who did a large cake sprayed red and later found pink all over her whole house - even upstairs - on her *ALL WHITE* furniture and rugs because she sprayed her cake near an airconditioning vent! !