Hey Kacey!
I think what most people on these boards will tell you is to just start looking for shows that need production assistants, assistant stage managers, and even smaller community shows that need SMs. In my opinion, the best way to learn how to be a stage manager is to do it. Find a regional theater near you and see if you can shadow someone, if there's a summer stock or community theater nearby see if they have internships or assistant positions, and make it known that you're willing to work and eager to learn.
Make sure you poke around the forums here, too--there is a ton of info on getting started and really anything else you may need/want to know.
Keep us posted on what you're doing, and good luck!