Usually when your temp drops you ovulate. You'll notice before ovulation your temps are lower, and after ovulation your temp rises and should stay risen until AF or a BFP....usually if you are pregnant your temp will stay up.
You'll know you ovulated because you'll have a low temp followed by 3 higher temps. If you are inputting all this into FF they will give you cross hairs on your ovulation day. I think today might be O day for me as I got a really low temp and I usually ovulate CD12, so hopefully the next few days my temp will rise and FF will give me cross hairs.
Check out anyone's chart here on the site, my FF chart is in my signature. Last month you can see FF gave me cross hairs on CD12, which was ovulation day.