I bought API's Quick Start, which is essentially the same as Prime's brand of bottled bacteria. I've read excellent reviews of Tetra's Safe Start though, so if you can afford it, I'd go with that. I opted for API because it was the cheapest name brand option.
You just follow the directions on the side of the bottle and cycle as normal, adding drops of pure ammonia not exceeding 4ppm at any time. That will kill the bacteria you're adding XD Or you can opt for an in fish cycle; its more humane using the added bacteria because your levels never gget very high. Buy a strip or liquid water test kit (liquid is more accurate, but to each his own) and test your water every day. When you have 0 ammonia, 0 nitrite, and some nitrate. For me, this process happened in a matter of days with the API bacteria, but I let it sit a little longer and added some more ammonia to make sure that the bacteria were doing their job (eliminating all ammonia added, in a cycled tank you should always have 0 ammonia).
I think I answered all your questions lol. Let me know if you have any more. I absolutely swear by this stuff now, its the best :)