Step 1
Separate the Power (18/2)
from the coax cable

Step 2
Remove about 1/2" to 3/4" of the outer jacket
Making sure to leave the copper brad.
Slide a crimp collar over the cable

Step 3
Spread out the copper brad an cut back the white insulator so that about 1/4" sticks out.
Then cut the center conductor so it is about 1/4" longer the the white insulator.

Step 4

Slid the BNC connector on to the center conductor making sure the center conductor goes into the connector
Make sure the center connector does not bend at the end not penetrate the back of the BNC connector

Step 5
Slid the crimp collar up over the copper brad up to the BNC connector

Step 6
Crimp the collar tight, so the BNC Connector can not be easily pulled off the cable.
You can trim off any remaining copper brad sticking out of the joint.