milktuds hit the nail on the head...
to gain that ammount of weight, its like me saying ok in 3 months time I want to be 150kgs... it takes years to get there, steroids don't make you (big) diet, rest, training, etc do.... steroids do help you become anabolic so help you repair your fibres quicker.
plz dont thumb suck a figure an think you will be there and just use the steroids for 3 months..... it took me a few years to gain 20kgs, so good luck with that unless you looking at holding allot of fat, but 20 kg muscle? goodness me!
"Whether You Think You Can or Can't, You're Right"--Henry Ford