great question I wasn't sure if I was doing it right either but found this online:
Tire Placement on a Stationary Trainer
Stationary trainers are known for eating away at rear tires because of the pressure used to press it against the drum. Since the bike doesn’t move or lean like it would outdoors, all this pressure is concentrated on a very small portion of the tire’s tread, leading to a worn out tire.
You can’t completely avoid this, but setting up the trainer properly will help maximize tire life and riding comfort.
First, make sure things are clean. Wipe down the tire and roller surface using isopropyl alcohol.
Second, inflate the tire to its maximum pressure. This should be about 110-130psi.
Third, tighten down the roller.
Typically you tighten things down until the roller is just tight enough on the tire that it doesn’t skip when you ride. It should be no tighter than is necessary.
Start out by tightening it down some, just until the drum touches the tire. Then give the tire a quick tug and see if it slips. You should pull in the direction of rotation, i.e. up and back when pulling from behind. If the tire slips, tighten a bit more.
Once the wheel no longer slips when yanked by hand, get on the bike and ride. If the wheel skips, tighten the knob a bit more. Repeat as necessary.
Like I said, you’ll still get tire wear, though. That’s the nature of the beast known as the indoor trainer.
Your best defense is good tire selection. You could use cheap, heavy tires or invest in a Continental Trainer Tire that is made specifically to last long on an indoor trainer.
If you’re using a nice, expensive tire on your indoor trainer, that’s a bad idea! You’ll waste a lot of money!
Lastly, after your workout, loosen the drum so it’s not pressed against the tire. If you leave it tightened down when not in use, the tire will develop a flat spot and will ride terribly.
Put these tips into action each time you set up your indoor trainer and you should have less hassle, more comfort, and increased tire life.