You neither mentioned the OS nor if it is the app or the extension you are asking about.
So I assume this is for Windows and a browser like Google Chrome.
Some basic information on keyboard shortcuts can be found here:
Something that unfortunately is not mentioned there is that pressing Ctrl + Shift + L repeatedly will loop through all available logins.
Furthermore there is Ctrl + Shift + Y to select the Bitwarden extension. This is especially helpful if Bitwarden has not been unlocked before.
If the hotkeys do not seem to work see here for some more information: