Wrong place for this really, should be in
Absolute Beginners.
However, after planting a seed, the plant needs to grow for 7-8 weeks under 18 or 24 hours of light per day before reaching sexual maturity. At any time after this, you can chane to 12 hours of light per day to induce flowering, which takes around 2 weeks to begin. Once flowers appear, it usually takes around another 8-9 weeks until it's ready for harvest.
17-19 weeks then for most common Indica hybrids from seed.
Flushing comes right at the end, and a simple
search will tell you all you need to know.