I very amateurly (if that's a word) bodybuild to some degree. The best thing you can do is limit your drinking/eating, watch what you eat, drink lots of water, and do stuff.
Watching what you eat means less eggs and bacon, more porridge/real cereals/fruit. Less fast food more lean meats, salad and veg. Less bad fats, more good fats (avocado, olive oil, etc.).
Do stuff means get a gym membership, go there 3 times a week, don't go 2 days in a row. Sit on the bike for 15-20 minutes and push/lift weights. Compound exercises like squats, deadlifts and bench presses are the best for burning energy (and building strength), but make sure you learn how to do them correctly before attempting. Having a gym membership and seeing money deducted from your bank account is usually enough motivation to actually go there and make use of it.
I could crap on for a while but I think I'll stop here and go to sleep.