From your web browser, go to one of the following addresses:
http://192.168.0.1
http://192.168.1.1
Enter your current credentials. IIRC, they are probably just 'admin' and 'password' unless VM supplied you with specific ones.
Then it's really just a matter of going to the Wireless page and changing things.
What make and model of router did they supply you, AAMOI...?



