sigh i need HELP

I'm pretty solid at and also enjoy writing, I used to wanna be an author until roughly 14 before my focus completely shifted on drawing, now I only write for school but I'm still told I'm good at it.

I've really been wanting to get into writing for fun but have absolutely ZERO clue how to start

the types I've been interested in is short stories and fanfic (probably only AUs because following the actual plot of a show in accurate detail is uhhh too hard) 

of course writing a fully fleshed out story with OCs (I've yet to fully develop..) would be amazing but I'd rather have a slow in steady start as ro not burn myself out before even properly getting into it

can anybody give me tips as to how to get started and keep on going? would be highly appreciatedddd