How to log in to new installation of Grist Desktop

I’ve installed Grist Desktop from Github. It automatically logs in a user You, and I can’t get away from that to log in and access my own data. If I log out and then hit sign in, the app automatically logs in the same user. What am I missing?

I have the same question - am I missing something obvious?
Or is this a standalone instance NOT linked to the hosted app?

I have a similar question. I installed GRIST desktop for mac (x64 version) and chose a screen name. I am trying to start over with a fresh install. After I uninstalled GRIST, then re-downloaded and re-installed, it keeps seeing my original sign-in name. Where is this stored on my mac? How do I get GRIST to “forget” my computer so that I can start over as if I had never installed it in the first place? (I assumed unistalling would handle this but it doesn’t).