It's just common sense really, loadsa meat, egg, fish etc along with carbs (preferably complex carbs like brown pasta, brown bread, brown rice etc etc....). If you've got a very fast metabolism then it probably won't matter about going for complex carbs, just go on a "See Food Diet" ie you see it, you eat it

Train hard & to failure, only once a week per bodypart. If the gym you know is a decent one then they will be able to help you with the finer details of all of the above.

As far as supplements go, weight gainers, protein powders, creatine etc do help but if you're only just starting off then I'd suggest just eating a decent diet & training hard for several months until you hit a plateau & then try supplements to help you get past it, along with changing your routine fairly regularly.

HTH's

Cheers,
Ian