How to fix my bike?

Is it a single-speed bike? If you have multiple speeds and only one of the rings are worn out then you can shift to another gear and not ride on the worn out one anymore. That's depending on your situation and whether the bike is nice enough that it's worth investing more money in.

Is your chain on the back? You'll need a new freewheel or cassette if the chain is on and not working. Does the teeth on the freewheel/cassette look worn down?

You need to go into a bike shop and they'll tell you how much it will cost to replace and whether it's worth it to do. If it's too expensive from them that it doesn't make sense, then you can still maybe find one on another used bike or something. You'll need the right one though. I don't know how good the bike is or how many speeds.

I'd play it safe.. good luck

Broken freewheel. Replace

Have somebody show you how.

Go to Google. Type in the words 'bicycle shop' with your 5 digit zip code. Pick one.

a bicycle shop will have the answer

Sounds like the pawls in the freewheel or cassette are shot. Bicycle shop time. Find one - go there.