Airport Express Extending Unsecured Network via WiFi
I am currently in a dorm and my room does not have a great connection. I'm trying to use my express to extend the wifi to get a better connection. Am I able to get the express to connect to the wireless network and then rebroadcast or do I have to hook it up via ethernet first in order to extend the network? I've tried creating a new network and then switching to extend. It allows me to pick the unsecured network but then says there was a problem extending it. Any help would be greatly appreciated.
MacBook Pro with Retina display, OS X Yosemite (10.10.2)