want to gain weight!

eve
Ik that usually people try to do the opposite, but I don't feel healthy or good the way I am now, and I don't like being thin. I don't have any illnesses related to that, and also I eat a lot... but I just can't gain weight, and I want to. If anybody has any normal tips or methods to gain a few kilos, I'd really appreciate if you shared them with me! 
(No "jokes"/hate please)