I think they were mainly only included on models that shipped with backhoes on the 3016.
They're bolt-on, but much needs removed to access and plumb everything. On most units, the seat, operator platform, and floorboard comes out; and on some the fender comes off too.
To plumb them you disconnect the 3 point hydraulic feed from either the pump, or if equipped, the front loader valve. The line that went to the 3 point you'll connect to the new spool (which is the control valve for the rear remotes), and from the new spool you reconnect the 3 point with another line they provide.
You'll mount the new spool under the right side of the seat and the control handle will stick up through the operator platform beside the seat, and there will be lines that go to the rear of the tractor where the remote ports mount.