first be consistent.
if u slack in any area of fitness u only slow the goals u want to reach. or u may stop growth all together.
try lifting threes days a week. resting between days. (for example) Mon., Wed. Fri. u work out. Sunday, Tues, Thurs, and Saturday u rest. u could try a full body workout doing an exercise for each part body part (chest, back, shoulders, legs, biceps, triceps, and calves). 3sets (rounds) of about 8-10 reps. per exercise. try not to exercise more than an hour at a time.
Third, check your diet.
Do some research into diets for slim guys wanting to get big. (try bodybuilding.com) u need to make sure u are eating enough protein for the size u want and getting enough calories in ur diet. calories are important to fuel the muscle building. protein is important for the body to have something to build with.
make sure ur getting enough sleep. i think its 8-9hours a night. make sure u go to bed around the same time and get up around the same time everyday. this will train ur body to know how much time it has to grow and repair. all ur growth happens while u sleep.
fifth set short term goals.
set mile marks on a calender. like i want to bench press "x" amount by "blank" date. make ur goals realistic so that u can achieve them.