setup airport wrong, now scan doesn't find it. how do I fix?

I would suggest that you perform a "factory default" reset on your Time Capsule. This will get the TC back to its "out-of-the-box" configuration. This configuration would broadcast an unsecured wireless network with a Network Name of something like: Apple Network NNNNNN. Once you can connect clients to this wireless network, you can use the AirPort Utility to make any configuration changes you require.

The factory default reset does not require that you access the TC via the AirPort Utility first. Instead, you would first unplug the TC from power. Then using a paperclip or similar object depress and hold in the reset button. While still holding in the button, plug the TC back into power. Hold the reset button down until the status light starts flashing rapidly then release the button. You may have to perform these steps a few times to make sure the reset "sticks."

Once you have successfully reset the TC, temporarily connect your computer directly, using an Ethernet cable, to one of its available LAN (opposing arrows) ports. You should now be able to access the TC using the AirPort Utility.