The hole is number 1 on this pic.
You want to release the lever ( near number 3 ) so the notches rotate counter clockwise ( number 2 ) until you can put something through the hole ( number 1 ) to lock it in place and keep the spring from forcing it back clockwise. It can be a little complicated.
What you are trying to do is get the cable to come out the bottom of the car as far as possible.
When you push the handle button it releases at number 3. It can be a PITA to turn the assemble counter clockwise. It's easier if you have someone under the car pulling on the cable while you press the handle button and try to stick a small screwdriver through the hole at ( 1 ) and the hole in the black metal part that the actual handle is connected to. I don't know what or why they are saying to drill the hole larger. I don't think I've ever done that.
It's like releasing a ratchet strap that has spring tension on it. If you have someone press the button on the handle you should be able to connect the cables under the car by pulling it.
The technique I use is to install the T bracket on the short cable coming from handle. Then I place vice grips or pliers around the short cable behind the bracket. Not on the cable but around it. Pliers can damage the cable. Have someone push the handle button and pull the pliers, bracket, and cable towards the back of the car. It should give you enough room to get the cables coming from the calipers inside the bracket.
