Time Capsule and Wirelessly Extending a Network

So I just cannot seem to find the right string of words to make google find the answer to my problem. So the short of my issue is I am using my Time Capsule to extend my currently existing wireless network. And I have a linux box, whose wireless drivers are not working for me. So I have connected an ethernet cable from my linux box to my time capsule. However, I cannot get my time capsule to connect my linux box to my network.

How might I go about getting my time capsule to connect my linux box to my network. Currently my connection sharing is stuck on Bridged, as in the airport utility will not let me change it.

Thanks in advance for any help