Go to settings. Then there are choices like Security, Privacy, Profile, Nostr. Go to Nostr, that is where the npub and nsec are keyed in. I had an idea that it was safer to go through Nostr.
Discussion
Oh shit! I found that section on mine. I don't remember using that setting, but I apparently filled it all in at some point, probably for NWC. However, I don't have a problem with logging in.