If you cannot draw something well chances are that you won’t be able to paint it. So learn how to draw it first. If you can’t draw something, someone on Youtube probably has a demo video about it.
Watch demo videos on Youtube about painting and drawing.
Find a “hero” artist who paints the way you want to. Learn everything you can through the internet and libraries.
Go to your library and take out books about artists you want to paint like.
Get demo books at the library.
Practice as much as you can.
Don’t be afraid to make the same drawing or painting multiple times.
Make as many drawings and paintings as you can stand to even if the first 100 are bad.
Study art history.