[jabu]

Start -> Settings
Click the Connections tab, then select Connections.
If you have a connection that says something like Sprint, then edit it. If not, select Add a new modem connection.
Give the connection a name, select Cellular Line as the modem and hit next. When asked for the dialup number enter #777 and hit next.
Now it will ask for your user name and password. Leave domain blank.
Hit finish and you should be good to go.

NOTE: If you don't know your PCS User and Password you can get it by logging into you account on Sprint's website. Once logged in, click the "Settings and Passwords" tab.