Thanks! I'll try that. Right now I'm using it to connect my Samsung SmartTV to my wireless network using the Ethernet cable.I used Airport Utility and selected "Join a wireless network". I selected my network, the one used by my primary router. You'll need to enter your wireless password. There should be an option to extend your wireless network. If it's an older version of the Airport Express, you may need this utility. The new Airport Utility doesn't work with older express units and the older version won't launch without the launcher available for download on that page.
This appears to be a good tutorial on the process.