no you cant switch it to flowering yet. you must keep it in vegetative state for about 4 weeks, then you can switch to 12/12. once in 12/12 it will remain this way for about 2 months. so the soonest you'll harvest will be around the end of April. as for the lights, MH(metal halide) is ideal for vegatating while HPS(high pressure sodium) is best for flowering. do you only have one plant? if so, remember chances of it being female are 50/50 so i'd suggest germinating some more seeds. good luck