Installing the donor buckle onto the recipient seat is essentially just reversing the removal process. First, I attached the cable to the seat bottom. Next, I bolted the assembly to side of the seat. Finally, I threaded the wiring through the seat bottom and zip-tied it in place.
Zip-ties ready to go on.
Wiring zip-tied in place.
Now, reattach the seat cushion and reinstall the seat by reconnecting the seat buckle connector to the wiring harness and bolting the seat in place.
You're all done ... unless you actually want to USE the car. You didn't forget about the battery cable, did you? Also, you may need an SRS reset tool to turn out your warning light.
NOTE: I'm not an expert, a master mechanic nor factory-trained technician. Messing with airbag systems may be hazardous to your health, wealth, and well-being. There is apparently a way to disarm the seat buckle assembly so that it won't blow up in your face (see Pelican Parts tutorial), but mine doesn't appear to have that feature. Proceed at your own risk. YMMV.