You don't boil the grains. That will release tannins from the grains, and increase the bitterness beyond what most people will drink.
Mashing is more like steeping, in this case, at 150*F for just over 75 minutes. Your sparge temperature is 180*F. This is your wort mixture. You boil that for 60 minutes, adding the hops in a countdown style (0.5oz Centennial at 60 minutes to end of boil -- immediately, 1oz Cascade at 10 minutes to end of boil -- 50 minutes of boiling, and 1oz Cascade at 0 minutes to end of boil -- as soon as you turn the burner off).
You also want to be able to cool down the wort mixture very quickly, whether using a wort chiller, or putting your metal pot in ice-cold water. Then you can put in the yeast.