How do you gain more weight

My parents keep telling me that i’m skinny and just bringing me down about it. I’ve told them that I know and I hate it and all they tell me is just to fix. I don’t know how

My appetite has been bad with every now and then there’s a day where i’m hungry asf but then the rest i can barely eat an egg.

I’m 5’5 and 50kg, i’m not overly skinny, i don’t think. I also have a fast metabolism