Currently the Realm Browser doesn’t support accessing databases directly on the device, so you need to copy the database from the emulator/phone to view it. That can be done by using ADB:
adb pull /data/data/<packagename>/files/ .
That command will pull all Realm files created using Realm.getInstance(new RealmConfiguration.Builder().build()) . The default database is called default.realm.
Note that this will only work on a emulator or if the device is rooted.