To build on Twister25's post, the first thing you'll do is add in a given quantity of water to make the mash. This can range anywhere from 1 qt water per pound of grain to 1.5 qt/lb (other ratios are possible, but this is the most common range). What you are shooting for is to get the grains plus water to the given mash temp, but you have to keep in mind that the grains are cooler than the water so mixing water and grains will result in a cooler combined temp. Therefore you'll need to heat the water (the "strike water") to something higher than the given mash temp. I know my system needs between 8 and 10 degrees F more than the desired mash temp (learned through trial and experience) to hit my strike temp when the grains are added in. No idea what your system is, what the thermal efficiency of that system is, what the ambient temp is, etc., so your temps may vary. Experimentation is the best way to learn (imo).
After you mash (which in your recipe is for 45 minutes), then you have a choice of sparging methods: fly sparge or batch sparge. Expanded discussions of both methods can be found on these boards.
In the instructions you quoted above there doesn't appear to be any kind of "mash out" temp difference, so I'd heat the sparge water to the same temp as the strike water. You'll need enough to hit your preboil volume (the volume of liquid wort you start the boil with). Again, you'll need to know the specifics of your system to figure out how much preboil volume you need (I know on my system I need about 6.8 gallons of wort to end up with 5.5 g of post boil wort). The reason for the additional liquid is that you lose some volume to boil off, some to trub in the boil kettle, some to dead space loss in the BK, and some to trub in the fermenter. Again, trial and error is probably the best way to figure this out for your particular system.
After you boil (which is probably for an hour, but check the recipe), you will want to cool the wort before pitching the yeast. If you are doing an ale (likely since the ferment temp is 68 F), you'll want to chill the wort down to at least 75 F before pitching. Higher temps can stress the yeast (leading to off flavors) or even stalled fermentation. There are various methods of chilling - ice bath, immersion chiller, chill plate, etc. A search of these boards will tell you all you need to know about this.
Once you get down to pitching temps, you'll want to keep the beer as close to 68 degrees as possible. Again, you have choices - swamp cooler, fermentation chamber, cold basement (if you have one) etc. Significant variations in temp will lead to different flavors as temps impact yeast performance. Of course, yeast strain will also contribute to flavors, attenuation, etc., but that's another post.
Do your best to keep the beer at the proper ferm temps until fermentation (and conditioning if you do this - and it's generally a good idea to do it) is complete.
That's a very basic overview of the process - there's much more detail that could be delved into on these topics, but hopefully this will help. Welcome to the obsession.
