So I was using a basic 'if authenticated user' placeholder rule for Firestore when I started using Geofirex. However, when I try to query/use the database with geofirex, my security blocked it. I'm currently running without any rules for the sake of development, so I know everything works, but I have no idea how to add rules to allow this library or have the library identified with the user. Is there even a way to do this?
If a library runs in the same process as the rest of your application code, there is no way to set up separate security for that library. All requests coming from the application are (and should be) treated equally, as there's nothing that inherently makes the library code more trusted than the code of your own application, or the code that malicious user may write.
What you can do is creating an additional collection that only contains the location of each object and its key. You could then point Geofirex to that collection and allow read-access to this data to all users, while securing access to the more sensitive other data about each object. This is what the original GeoFire libraries from Firebase did, and while it leads to more code (to read the additional data objects), it makes it much simpler to secure data access.