Well the ap web interface will need to be on the same subnet as your 2wire router. So if your router is 192.168.1.1/255.255.255.0 make your ap ip address 192.168.1.2/255.255.255.0 with the default gateway of 192.168.1.1. That will put the ap on the same network. Any time you need to configure the ap you will use .2
Then you will need to configure the wireless to bridging mode, enter the ssid and wireless security settings that is setup on the 2wire router. (something you will want to look into the manual again) After the ap successfully connects to the wireless network then your xbox 360 will get an ip address