My tips and mini tutorial on how to go about this. No tl:dr so read it all not half!
Step 1: First you need to see how much you can lift. Stick with the resistance machines for now and try to lift as much you can without too much stress. If you are lifting a weight and your eyes are popping out and your shaking then it's too heavy. Find something you are comfortable with.
Step 2: Once you have found the heaviest weight you work best on then lift that weight 2-4 times. Do this with all the machines (Or just the ones for the areas you are trying to work out) and repeat. The more you lift the fewer reps you are gonna want to do.
Step 3: After repeating Step 2 several times over the course of a few weeks you will see changes. This is what I learnt and I am glad I did as for example on my legs I went from lifting around 40-50kg to 120+. Of course, to some, that may be nothing but at the end of the day if you are lifting more than you did last time then you are good. But make sure you increase the weight gradually. Don't add on 5kg each day. Maybe 5-10kg a week or two?
Things to keep in mind!:
1. If you want to get massive you need to lift heavy weights and fewer reps. You gonna want to repeat this.
2. Don't go home and eat shit. Get plenty of protein for your tissue to repair itself. It ain't gonna repair itself with chocolate and ice cream.
3. Make sure you can actually lift the weight you are trying to lift. You shouldn't be shaking or showing legit signs of a struggle. Don't hide it either. Nothing wrong with lifting smaller weights when you start. You gotta start somewhere.
4. Make sure you eat right before you go to the Gym. I have made the terrible mistake of having nothing to little to eat and I felt like I was gonna pass out and be sick due to low blood pressure and energy. Not worth it.
5. Last but not least, Make sure you plan your fitness sessions (Days to go and how long for) and maintain motivation! I have had many mates try and get massive but stopped halfway through and lost it all so you need to keep going and trying!
(Mini tip) Don't and try and be that guy who tries to show off. You will just look like a tit and will probs look special. Just go in there, lift what you are gonna lift and go out, simple. Also, I highly reccomend Cardio beforehand. Good for warming you up and helps you lose weight which will help the muscle show better. Even if you are already skinny af being able to run further and longer ain't a bad thing is it?