How do I gain weight?

Most girls don't want to be skinny and kill for curves. My best friend who's always been a big girl though I was crazy for wanting to gain weight. I told her, "I've been bullied and criticized for being thin all my life. We don't always have it easy. Most girls do NOT wanna be skinny and not every girl wants to be skinny and have flat bellies. Thin isn't even in anymore. I'm tired of being skinny and it's hard to gain weight. Consider yourself lucky to be curvy. That's probably why most girls and women envy you. You're not fat. I wanna be able to fill out and look good in clothes."
I'm 4'8 and 96lbs. I'm too skinny and I can't gain weight!!! 😭😭😭😭😠😠🤬🤬🤬
My friend envies skinny girl and she shouldn't. She's 5'10 and 226lbs.