If you are new to lightning, chances are you only have outbound liquidity from channels you’ve opened - this means that you are only able to spend at first (once you spend, you now have the ability to receive, but it’s likely more limited than you’d want).
There are a handful of places to find Inbound Liquidity:
- The Umbrel Community Forum
- LightningNetwork+
- Plebnet is a good resource as well
- Lightning Loop, which is a service available in a few Lightning apps on your Umbrel (like Lightning Terminal)