Turn Time Capsule from router into wireless backup
So a while back I wanted to disable the router part of my old TC and turn it into simply a backup drive and do it via ethernet. I was successful in disabling the router part but it was backing up wirelessly (don't ask me how, it just happened that way). Then, I needed to turn it back into a router so I was successful in doing that. But now I would like to disable the router again and replicate what I did the first time but I can't remember how. I would like to use the TC as my backup drive and do it wirelessly but can't seem to figure it out. I've read other threads about similar situations but they are never the same. I turned off wireless and switched to bridge mode on network but I can only use the TC via ethernet connected via WAN to the router (Orbi) LAN. Suggestions will be appreciated.
iMac (21.5-inch, Late 2013), OS X Yosemite (10.10.5)