PIX 6.2 vpngroup syntax help

Greetings,

I need to change the

vpngroup vpnusers dns-server 10.10.10.1

to

vpngroup vpnusers dns-server 10.10.10.2

I'm a newbie that needs to make a local backup copy of configurations and change the dns server ip.

I should go from enable mode to configure mode, correct?  What is the exact syntax of the command?

Thanks for your help.

J.H.