Simply put:
Get into a gym.
Start squatting, deadlifting, bench pressing, overhead pressing, and do chin ups, rows, dips, etc as well. The first four are the core exercises though.
Research routines, keep them simple and based around the exercises I mentioned above. No need to be doing weights any more than 3 or 4 times a week.
Eat lots of protein. Eat 5-6 meals a day, say every 3 hours or so. Each meal should consist of a lean protein source (chicken breast, turkey breast, portion of lean beef mince, 4-5 eggs, tin of tuna, salmon fillet, etc.), a carb source (pasta, rice, potato/sweet potato, oats, etc.), and loads of veg. And milk is good, drink lots of milk.
Read the beginner articles found on this site. Do your research, work hard in the gym and eat big, and there's no reason you can't pack on muscle.
Good luck
<message edited by CitizenKane on 12 March 2010 19:46>