weight gain help

can someone please give me detailed help to gain weight? after I had my baby I lost over 20lbs and I was already a petite person.. so i’m even smaller and very insecure about it.. I at least want to gain the weight back that I was it’s been extremely hard.. and i’ve tried a lot.. I know I have to eat even more calories but will anything else help tremendously? I need to know if I should eat every few hours snacks in between etc.. if anyone would thank you!