I did this by putting food on each level. Sentinel went first looking for the treats. Antares hung back.
A good long scratch by the little kitty.
Antares makes his move.
I bought the cat scratcher at the Oregon Humane Society which is a good place to find them. They have various sizes, they are a decent price and last a long time and by purchasing from the Humane Society, your money goes to support their many programs. Plus you get to say hello to all the cats temporarily residing there.