I am a student and am 18 years old. I’m 6 feet tall and weigh about 72 kg.
Although I am mainly quite thin, most of my fat is accumulated around my waist and stomach (my chest and arms are skinny and ribs are partially visible).
Do you have any tips on how to gain mass overall on my body that is on the chest, stomach, arms, legs etc?
in order to add muscles, a balanced weight training routine is the best way to accomplish that together with a healthy diet.
However, I would suggest that you see a physician. The way you describe yourself with fat around the waist and stomach is not what I would expect at a person your age. There are some metabolic disorders that can manifest like that, and it would be a good idea to rule that out.
I wish you good health.