Yes, you can eat foots that are high in fat, IF they are high in protein. Such as meat.
AVOID foods that are high in simple sugars and in corn syrup. Like ice cream. Throw that soda away and grab some milk. Seriously.
When you get older and your metabolism changes you will need to adjust your eating habits, but for now, eat lots of meat to get big!
Note: You can mess up and eat hot dogs, ice cream, and other crap occasionally and it isnt going to kill you. But cut it back.