If you are very skinny and you want to bulk up, then you need to learn from my personal experience because I was once very skinny.
There are people who are naturally gifted, and they can get buffed just by staring at the weights.
You do not want to listen to them for advice because what works for them will not work for you.
Too many beginners believe that you need to do a lot of reps and spend a lot of time at the gym to get results.
That is far from the truth because you are only going to suffer from overtraining.
I used to do very high reps with light weight bicep curls to go for the "pump" effect to give me bulging biceps, but that is only a temporary effect that can only fool yourself.
Lifting light weight will not help you build muscles.
You need to focus on compound exercises.
Examples are deadlift, squat, bench press, pull-ups, parallel dips, lunges, shoulder press, etc.
These exercises will let you lift heavier weights to build bigger muscles.
Make your last set as the heaviest one.
Make all your previous sets a warm-up to lift your heaviest.
You do not need to do 5 sets of incline bench press, 5 for decline, and a bunch of chest flies like bodybuilding magazines tell you to do.
If you are very skinny, then you need to stop paying attention to bodybuilding magazines, and listen to people who were just like you from the beginning.