To delete a bridge, select the sensor icon in the app > choose the bridge tab > select the "Delete bridge" button. Once you've done this, while the bridge is plugged in, take a paper clip and restart the bridge. This will disassociate the bridge with your wifi.
Note: When resetting your bridge, make sure it's plugged in while you hit the reset button. The light will turn blue.
To add a bridge, make sure you are on your 2.4ghz wifi network, select the sensor icon > choose the bridge tab > select the "Add bridge" button.