Installing a cable grip in a floor usually takes two people. One feeds it in while the person inside screws on the locking ring.
This instructable shows how one person can do it easily.
Bend a hook on the end of a wire/rod then bend the wire into a horseshoe shape.
Place the locking ring over the hole to be used.
Feed the newly bent rod into the locking ring.
Bring the hooked end back through another hole and place a CGB onto it.
Feed the CGB through the larger hole by retracting the bent rod.
The hook prevents the CGB from falling off.
Guide the threads of the CGB into the hole.
While holding the CGB in the hole with the bent rod, screw on the locking ring.
Afterwards, fiddle with the hook and pull it back through the CGB. Tighten the lock ring and you're done!
If you have only one hole or to finish the larger ones, simply thread a string or rope down the hole with a hooked rod/wire attached. Go downstairs and place the CGB onto the hook. Go back upstairs and pull the CGB into place. Screw on the lock ring and tighten.