try spraying it with something they don't like. I believe citrus sent are repellants for cats
Good luck. LOLOLOL. First advice is not to put tinsel up. Seriously dangerous if they eat it. Tie the tree to the baseboard using eye hooks in the floor molding and use fishing line to anchor it in two places to the eye hooks. don't put dainty, chewable or breakable ornaments low. (people look at eye height first anyway). Wire the lower ornaments on the tree by twisting the wire hangers onto the ornament and tree not just hanging them on the cheap hooks. When you cat goes near the tree spray them with a water bottle and say no. The only other option I can give is put the tree in a room you can close a door on.
If you have a live tree cover the water in the basin since they WILL try to drink it no matter how much is in their own bowl.
Well I have 6 and mine don't care. However they do like to snuggle underneath it. Years ago I had a cat that liked to climb the tree. So I did away with glass or fragile ornaments. Was an "open concept" home so no doors to close. We just braced to the wall so it wouldn't topple over. And I picked up and put back the ornaments that she knocked off every day.
I used to spray mine with a deterrent I got at the pet store.
Never ending struggle! I just put ornaments up high, and then they lose interest after a few days.