A few suggestions...
1. Over the next week or so, monitor your water parameters closely. If the Bio-Spira "takes," you should start seeing nitrates very soon. If you go a week and still no nitrates have appeared, it probably means you got a bad batch of Bio-Spira.
2. Especially if you do see signs the Bio-Spira is working, consider getting another female or two. In general, livebearers like guppies should be kept at a ratio of 2-3 females per male. The reason is that the males tend to be in a mating "mood" almost all the time, and with just one female, sometimes she can be harassed too much by the male. With multiple females, this gets spread out among them all and so it is less likely you end up with an overly stressed female on your hands.
3. It is very likely your female is pregnant. Especially if the pet store kept males & females together in the same tank. How are you going to handle this? You could do nothing, and just let nature take its course (i.e. let the parents eat most if not all of the babies), or you could buy some nice thick floating plants for the fry to hide in, or even buy a breeder net. The problem with the latter option(s) is that you might end up having *too many* of the fry survive...too many, that is, to fit in one 10 gallon tank. At which point, you're doing to need to buy a bigger tank.
4. As for lighting, a lot of it is a matter of taste. In the wild, you can figure tropical fish are probably used to ~ 12 hours of light a day, give or take. Most people would aim for something around that, maybe 10-12 hours a day, in an aquarium. It is not really a huge issue unless you start getting algae blooms in your tank.
Congrats on the fish! Keep us posted, and if possible, post a picture of your guppies.
