Run the program. and browse to a GameMaker Studio project file (.gmx). you can also change the images, Title. and TitleID and then your game will be "compiled" for PSVITA and saved as a VPK to whereever you choose to save it
Note: Games are compiled as "GameMaker Studio 1.4.1763" even if your using a newer version. the game created by GayMaker will allways be this verison. if you want a newer version. find a game thats using it that is also NOT YoYo Compiler. (Look for CODE block in game.win)
Also: Shaders do not work, it throws some "File not found" error whenever it trys to compile shaders probably because of the vita's properitary GXT format. . . its probably looking for some file that'd be in the offical export tool. but we dont have that file. so.. just dont use shaders i guess?