Thank you for posting your question to the Ask Me Help Desk.
I would start looking for ways to volunteer your time at a local gym, High School, or Community Education program.
If you can find a place that is willing to pay you, well of course that is better.
I would suggest shadowing a coach so that you can pick up some experience with technique and pedagogy. Depending on the age group and level of the gymnasts you are working with, you can probably get some practice spotting skills as well.
As you spend more time in the gym you should be able to begin working with more groups.
Start reading some books and magazines on gymnastics to learn some new drills and teaching tips to share with your classes.
You should also consider taking some coaching and safety certification courses as well as CPR and First Aid training.
Be enthusiastic and show how much you are dedicated to the sport.
I have coached for 16 years so you can feel free to come back to the Ask Me Help Desk and ask a few questions from time to time too.
Let me know how things work out for you.