For starters, you have to be on OS 3.0.

Method 1 (Cydia)
1. Install the file "ActivateMMS2G" from the ispazio repo in Cydia.

Method 2 (SSH)
1. Using SSH, copy the file mms2g.deb (attached) into iphone folder, for example /var/root
2. Then in same folder (/var/root) in terminal input: dpkg -i mms2g.deb
3. Reboot.

Method 3 (SSH)
1. Extract files from Patch.zip into folders same as arhive.
2. For CommCenter chmod 755.
2. Reboot.
You can then adjust the apn, user, password, under Settings - General - Network - Cellular Data Network Settings.