Your MVP is a Discovery Device
If you've already built an MVP, use it as a discovery tool.
It can help learn who target market is and what they actually want.
Here's a fun acronym to help you remember:
MVP
as
Discovery
MaD.
How to do this?
Promote your product in places you wouldn't normally promote it. You may discover people you wouldn't have originally thought to target. Or people who use it in an unexpected way.