Welcome! Joining a gym is a great idea; I recommend it to anyone! Here's a good section with tips:
http://www.obesitydiscussion.com/for...eres-3689.html
Cutting all junk food out and unhealthy snacks is a great start! Eventually one of the things you should be shooting for is to eat fewer calories on an average day than your body burns on its own. Exercising will help you increase how many calories your body burns, but it helps to know what you're putting into it as well.
We're more than happy to help you figure that out.
