squat for big arms???
Yes.
To add 1 inch to your arms you need to add 10-15 pounds of overall body mass. The easiest way to do this is by performing the exercises that give you the most bang for your buck. Heavy compound free weight exercises. Direct bi work is not gonna do it for you. Heavy squats, deads, bench, rows, chins, military press, etc will add size to your whole body. If your diet is in order.
You should be eating like it is your job. Every meal should be a chore to finish and leave you stuffed. It takes a lot of food to grow and it is not easy to do. Those 20 pounds you gained are common when you first start training. the next 20 won't be as easy. You will have to work for it.