The "classical" or "traditional" way to login into Abacre Point of Sale is using username and password.
The detailed procedure is described here.
In order to still use such traditional login but to make the logins more faster you may use option:
Login by password only (username will be hidden)
This option is located on menu Configuration - Preferences - Shifts.
Check it option.
Restart the program.
After that on Login window username field will be hidden. Thus it will be possible to login just just entering the password. Note: in this case please make sure that the passwords are unique. In other words each worker has individual password.