How to gain weight

ray

Ik it's stupid but I been trying to gain weight for years and nothing works i am a active person I do food services so I'm on my feet half the day and I did soccer for the longest time but not doing it this year do to school and needing more hours for work what is the easiest way to gain weight I'm on the nexoplon birthcontrol which made me loose 10 pounds so now I'm 5ft 5" and 110ibs. I would like to gain at least 15 pounds