Once printed, feed the lightning end of the the cable through the bottom of the dock using the right hole. Move the end over to the middle then start to wiggle and push/pull the connector down into the center pocket. Once started, use your phone to push the connector down into the dock. This may take some force (try not to break the plastic.) It is a very snug fit and the connector will not come unless forced out. Route the cable in the channel at the back of the dock. The cable sticks out of the bottom of this dock because of the long strain relief on the cable. Someone feel free to tweak the design to fix this.
Remove your radio bezel and then remove the airbag switch. You can push the airbag switch into the dash and leave the wiring connected. Use two short (.5") screws to mount the dock in place of the switch. I edited the file after I printed it to add holes, however I printed it without them. When mounting the plastic has a tendency to split, but it will still hold the dock on just fine.
Once in place, route the usb cable to the back of your in dash stereo and reassemble.