here’s an article on how to hack your Linksys router to act as a repeater.
Your neighbor is in possession of router A. It is set to factory defaults initially. This is important because it shows the victim isn’t technically savvy and won’t notice your intrusion. You have router B, a Linksys WRT54G that you will be putting into client mode and connecting to router A. The final component, router C, is plugged into router B and acts as a wireless access point.