I started out about your size. The main thing you are going to have to do is learn to eat. I always thought I was eating a ton of food all day long until I counted it. Yeah, I was eating more than other people my size, but I wasn't eating anywhere near enough to grow.
So start keeping track of what you eat, count up the calories. You're going to want 500-1000 over maintenance, or just take your weight and multiply it by 20. You may gain some fat doing this, but you need to pack some serious mass onto your frame, right?
When you first start bulking, you will be eating so much food that you won't ever want to actually eat. There will be days where you will have to force yourself to eat, to the point where you will want to vomit - but you won't vomit, because you won't want to waste the food.
Don't worry though, eating a lot will get easy after a while. I can pack away tons upon tons of food now with ease.
Get the eating sorted. That's what is holding you back. You have to eat a lot of food if you want to make size gains.
HST is a great routine to follow for building mass. I'd suggest you do as little as possible. Stick to only 3 days a week and focus on Bench, Squats, Bentover Rows and Military Press. Your workouts will be fast, hopefully around 30 minutes, but you want to push yourself. Don't go easy on the weight.
Just in case it seems like I'm pushing the eating angle too much, here's a frame of reference. I originally started out about 145 lbs when I first began working out. I worked out in a retarded manner and ate like a moron, and only gained a little bit. When I finally figured out I had to eat like it was my job, I finally started to make gains. Last year, I began HST for the first time in January at about 180 lbs and hit a peak of about 225 lbs earlier this year.
If you started bulking properly now and continued for several HST cycles, you could easily hit 180 lbs by the end of the year.