On the outside the fitting you removed, is it like a tray or "cup" where water fills the reservoir? Is the any garden hose type connection on the outside? I have never seen a Boler
without the street water set-up unless a PO has removed it.
Do you have any pictures?
But in general it is very easy plumbing, garden hose connection on outside (available from any RV dealer. Any faucet you like on the inside, you can use an RV faucet or a home bathroom, bar, or kitchen faucet. and then a water line between the two.