Deleting a wireless network

I just hooked up a faster router to my Fios router and moved the new router to the top of the list, but it connects to the old one sometimes. How do I delete the old router from the network altogether? Thanks

Open Network Preferences > Advanced - Highlight the network in question and click the '-' (which is right next to the '+')

Thanks a lot. I knew it would be easy, but didn't see that for some reason. I appreciate your help!