I have exactly the same issue.
In Drools Workbench 6b5 (what used to be Guvnor) I get the login screen, but no documentation whatsoever on how to log in or where to define accounts. The included docs are still fort Guvnor 5.5 :-(
Since it is now based on UberFire, i tried to find documentation for that, but i couldn;t find any documentation for that either.
Any help is very much appreciated!
I solved the problem. Some info for who may need it:
The default login/password is admin/admin.
This didn't work for me, because firefox had another password saved with the username 'Admin' (starts with uppercase), and was secretly 'correcting' the 'admin' username to get uppercase.
Removing the 'Admin' password for localhost:8080 in the Firefox password manager fixed the issue.
Hope this may help some of you.