If the OG of the beer is projected to be more than 1.040 or so, it's best to do a starter or use two vials. The package says it's good up to 1.060 or so, but in my experience it's hard to get super fresh yeast that hasn't lost some viability in shipping.
In any case, pitch your yeast when the wort is cooled and after aerating the wort. I like to pitch at 60 degrees and let the temperature increase up to 65 during fermentation, but you should be ok if you pitch at 70 degrees or less.
Take the vial out of the fridge about an hour before you need it, and give it a shake to suspend all of the yeast. After that, open it VERY slowly. First just crack it open to let out the "hiss" and then open it the rest of the way and pour it in the wort. Don't stir or shake, just cover it with the airlock and leave it be.
If you shake the vial, and then open it, there will be yeast on your walls and ceiling but none left in the vial to use. (Ask me how I know this.

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