Welcome to Audioholics.
Your situation is exactly why it recommended to buy speakers first, and then find a compatible receiver / amp to drive them.
Understanding it's not a perfect world, here's my less than perfect answer.
If you've already purchased the speakers.... the way to use them without burning out your receiver would be as follows.
Don't try to listen at loud levels and forget about filling a large room with sound.
The louder you turn it up the hotter it will get.
Monitor the heat coming from the top of the unit, if it gets too hot, turn it down or shut it off.
Give it plenty of breathing room, hopefully it's not in an enclosed cabinet.
I'd add one or two flat computer fans on top, and pull the air up and out.
Judging from the lite weight of that Yamaha, it doesn't have much in the way of heat sinking.
Good luck and be careful out there.
