Setting up and Access Point Name (APN) for browsing with 3G
Normally you can simply insert a SIM card and you will be able to browse the internet using 3G. Sometimes, this must be setup manually however. Before you start, you will need to ask your carrier or Telco for your APN settings.
Once you have those, from your homescreen press Menu - Settings - More networks - Mobile networks - Access Point Names.
From here press the Menu key again (bottom left corner) and select New APN. Then fill in the details your carrier gave you. Then press the menu icon again and press Save.