Hi @Simey,
Welcome to the forum! I'm re-classifying this as user support, since this isnt a technical problem with the software. It sounds like you're working on a super cool project!
You can find reference files for the Silva and Greengenes databases on our data resources page. You'll need a representative sequence file and taxonomy file. Then, you can follow the tutorial for training your own classifier (use your primers rather than the EMP 515-806).
You can also follow the RESCRIPt tutorial to download and format your own database.
Best,
Justine