Also, there are many '101' books on drivethrurpg.com, the sponsor site. It's not hard to find RPG plot seeds, or short lists of ideas you can run with.
I would also suggest thinking beyond quests if you want more than one-off games. Books such as Engine Publishing's Odyssey: The Complete Gamemaster's Guide to Campaign Management, can help you think about the questions and steps necessary to keep enjoying RPGs over time.
And in Tabletop Roleplaying Open, well there are many list threads that can be of use. If you don't see any recent for the genre you want, you could start a new thread.
If you're new and you're struggling with writing stuff, I'd suggest starting off by picking some good adventure modules / a campaign module to run for a while. Reading modules other people wrote and then running them exposes you to their styles and builds literacy.
There are tons of quest idea generators at generator websites like donjon, chaotic shiny, and fantasy name generators. I find these quest seeds inspire a good place to start. Then it's about fitting it into your game and statting it up.