You need to provide him the NWC from your alby hub, you create that for each user and they just have to scan the QR or paste the NWC address. Done.

OK later I will update my alby guide, with more instructions to connect alby go and create sub-accounts etc. I think they have also some instructions on their manual page https://guides.getalby.com/user-guide/alby-account-and-browser-extension/alby-go/get-alby-mobile-app