Crankset

Not cranks, it's crankset. You must pose and follow the industry standards and say all sorts of pretentious things like this if you want to continue.
There are several types of bottom brackets depending on your frame. Mine took a 68mm (width) American thread. The older Masi I'm building takes Italian thread. The width, 102mm, 110mm, etc. is determined by the crank manufacturer and not necessarily by the frame you have. There are times when a recommended BB is so narrow that the crank arms will hit your chainstays or will give your heels so little room you'll need a wider one. Since the right side (drive side) of the BB cartridge has a fixed flange, it can be shimmed a bit for small adjustments. Go with what the crank guys say at first. Mine wasn't a problem and I suspect it isn't that common to have issues on production frames. I left the included spacers in place, one on each side, which began to groove the inner spider from the BB cups rubbing. This isn't visible and didn't compromise the carbon fiber weave but I wasn't very happy with myself. One shim would have been okay but don't space these types of BBs without careful fitting.
I used a Park tool for my BB. There are several types of BB tools. Get the one for your BB. This is for the Truvativ/SRAM GSX BB shell. The Shimano BB typically has 20 inner splines. Campagnolo has its own inner spline deal that will also fit the cassette on the rear wheel. Kudos to them for making a multi use tool. Then again, they should 'cause they are also the most expensive out there.
There are better BB tools than the one I chose. Pedros has them in a socket.

http://www.pedros.com/index

These can be used with your torque wrench unlike the Park model. Park tools are cheap and easy to find but not the best and not the most robust IMO. They even say things like, "60ft/lb is like 10lbs of force 12" from the BB." Hardly precise and equally unmeasurable. Use a torque wrench so you don't come apart on the street!
Shown here are the basics. On top is the larger ft/lb torque wrench and below, the in/lb. The hex sockets are a necessity. If you have only a bigger ft/lb torque wrench, no sweat. The common specs found in in/lbs can be easily converted to ft/lbs by dividing by 12. Sounds too simple to be true doesn't it? There are cool digital torque wrenches now that you can enter any spec into. Clicking these things up and down gets old fast but not fast enough to go buy new ones now. Cool story: I foolishly trashed my older Craftsman wrench, likely from using it as a breaker bar but I don't publicly remember. I was going to do a brake job on the girlfriend's car saving her/ her dad a few hundred bucks. I whined that I needed a new torque wrench first and what do you suppose I got in the mail? A brand new one! I wonder if Craftsman will replace the old one? Doubt it. Now it really is a breaker bar - an $80 breaker bar!

Staying off the subject I'll make a point on weight, the BB on top weighs 262g while the Campagnolo Record BB weighs 195g. One costs $17, the other, about $130.
You guess which is more. There is a .15 lb difference! You have to decide where to cut your losses or you will soon be bike poor.
Unlike the older style BB shown above, the GSX BB is basically a tube that holds the bearings in place.
Like Shimano's Octalink (for all the Ultegra/DuraAce fans), the SRAM crankset uses a fixed spindle on the drive side. Grease the bearing surfaces lightly and push it through from the drive side. BBs do have a right and left and the drive side has a larger bearing and seal. The drive side takes more direct force at this larger bearing so.......

Anyway, once through, slide the left crank arm on and install the bolt. Torque it to spec - in this case 425 - 478 in/lb (35 - 39 ft/lb). SRAM has a neat feature here. The crank bolt is inside an extractor cap so when you loosen the bolt it automatically pulls the crank arm from the spline. No need for a crank puller! Nice job!
This is also a good time to check the torque on the chainring bolts. SRAM uses a different sized hex on each side, I guess in case you have only one set of wrenches. I have so many accumulated that I have some in a box in a bag under the workbench and I still trip over whats left in the toolbox! You will be using a torque wrench and hex socket on one side anyway. 80-90 in/lb and these were all dead on.