It's possible the seeds are bad, depending on how they were stored. If you're planting outdoors, you need to consider how many hours of sunlight you get each day. Cannabis, if it's not auto-flowering, starts flowering when the days start getting shorter at the summer solstice. Cannabis indica is ready to harvest in about 6 weeks, and sativa in about 8. The plant needs a growth period (before flowering), which can last anywhere from 1 month to several. The longer it grows, the bigger it will get. You shouldn't plant before spring, and it's best to choose a spot with lots of sun and close to water so you don't have to water it often. Plant the seeds in several different spots in a hole about 2-3 cm (1 inches) deep, and don't press the soil down too hard. You could also germinate the seeds indoors and then transplant them to their permanent location, but that's riskier.