How to get Wi-Fi from my iphone 4s UNLOCKED?

A few days ago i bought an iphone 4s unlocked from gumtree and i wanted to buy a new sim card (micro) but i had to use my old one for now. I cut my old sim card (not micro) and it worked but when i go to carrier. I thought there was going to be more than three carriers ( telstra, vodaphone, optus appeared) i turned my Wi-Fi off and tested it but it did not work

You don't lock or unlock your Wi-Fi on your phone

Wi-Fi is a local access through home or business broadband services, and you can put a password on it, but it doesn't have to do with wireless services like you listed.