Use a harness with an o-ring to strap it to a pillow/cushion/piece of furniture in the desired position. If you don't have a harness, which I assume you don't, since you said this is your first toy, get an o-ring at a hardware store, and attach it to a couple of straps in any way you wish. If you want to do it right, you'd sew leather straps to it, with a buckle, but you could just feed any random straps or ropes through it and tie them far enough from said ring that the knots won't be in your way.

If the toy doesn't have a base, it won't stay in the harness, so then you'd need to create a base. That would involve drilling a hole in the bottom so you can screw something into it -- anything round that's wider than the O-ring would probably work. Some kind of rubber washer, perhaps?

Or, you could buy the Tantus suction cup and screw that in, but that would cost considerably more than you paid for this particular toy. You'd be better served to just upgrade the whole thing.

You could also buy something like the Liberator BonBon or Wing or Pulse -- those are all pillows with a built-in hole for holding dildos upright.

Whatever you do, if you're using a dildo without a base anally, it's not recommended, as the toy could get lost in an embarrassing medical emergency sort of way. Find a way to securely attach some kind of base to it, or, again, upgrade. less