The commands for adding a user name and password to the pix to authenticate locally to the VPN are:
vpdn group 1 client authentication local
vpdn username [whatever] password [whatever]
There are a lot of other settings required for a vpn to operate however, I need more information to really help you.
I recommend using pptp for a begining if you have 3DES installed on the PIX. This is an easy VPN to setup up and you can set up a VPN using 128bit mppe encryption in about 5 min. with MS-CHAP authentication allowing all windows 95/98/me/2000 machines to connect with no special client software.
You can e-Mail me if you like and I will give you a sample pptp configuration with a description of the commands if you are interested.
Regards,
Chip (chip@chehost.com)