I am confused about where to find any useful documentation on the Cisco site. I am caught in a loop when trying to find any command reference - pointing meto "IOS software" - is this what they mean ?

Networking Software (IOS & NX-OS) - don't know what to pick here

Can you point me to a good basic tutorial [here or elsewhere] for a 1941-k9? Capabilities and basic tasks.

My immediate task is a little housekeeping - removing defunct usernames and resetting passwords for our VPN users. I'd only been shown to add a user/pass, I don't even know how to list out the existing usernames