try researching on bodybuilding.com for workout plans.
3-4x/week workout days is all right. some articles even say that 2x/week is enough to build mass already.
just go with the proper form always whenever lifting weights to avoid injury and to keep on track with your progress and program.
for supplements, i read a lot of people suggested using creatine. it does help a lot with explosiveness but we aware that it dehydrates you fast, so always drink lots of fluids when lifting. for protein supplements, i used to drink nitrotech, it bulks you up relatively quick. i used to weight 140lbs but when i started using nitrotech my mass shooted up to 160 in a couple of months. in a year i was about 175lbs already. another good brand i know is celltech.
good luck! dont forget to stretch before and after lifting, its the stretch that stimulates the muscles to grow. and lots of rest!