I've made that recipe, and it IS really good!
It looks like you've picked the correct ingredients.
You just put the grains in a grain bag and steep for 20-30 minutes. You can add the grain to your pot when it's about 160 degrees, so that you can steep at 150-160 for the entire time. After that, lift the grains out of the pot and allow to drain back into the pot. If you want, you can pour some 170 degree water over the grain bag (it's easiest if the grain bag is in a strainer over your pot) to "rinse" the grain. It's not necessary, but it helps to get all of the goodness out of the grain. Throw away the grains, and bring the resulting liquid to a boil.
Then you can add your extract and bring to a boil again. Add your hops according to the schedule.
All extract beers with steeping grains are done the same way, so you can do that each time.