Seeing as everyone is bitching you Ahuron. I shall help you. First, I'll explain what each compoment is
Sprite : Graphics for characters, NPCs, Monsters, etc
Background : Graphics for the scenery
Sounds : You can guess
Timeline : Use this for scenes and events in your game
Path : Makes an object move on a certain path (Not recommended)
Font : Another guess
Object : The most important part of GM7. Objects. They can be anything interactive. Characters, NPC, Boss, Items, ANYTHING!
To add anything, right click the text in the left side menu (The one with all the stuff I read out) and click the Add ____ function (The ____ is what you want to add)
Tell me if you understand