Don't know what to do

So im 17 living at home. The problem i have is that i swim on a competitive level (3 times a week). While i swim i want to gain muscle but is that even possible? I also have no idea to what to train at gym. Mostly i want to look bigger.

To add im 177cm and 67kg. My dad usually makes healthy food but also buys fast food once a week, is that okay? The food my dad makes doesnt always contain a lot of protein but i get that from whey and milk products.