You're right, the second line on an ovulation tests needs to be as dark as the test one to be positive. Once it is you are about to ovulate so make good use of the time. As to when you actually ovulate could be anywhere from 6 hours to 24 hours after your positive test. So it's always best to BD as much as possible in the few days leading up to ovulation as sperm can last for a few days.
It is normal to have a temperature dip just before ovulation. When you get that it's a good sign you're likely to ov in the next day or two so that's when it's good to do your OPK's. Although as temps do go up and down a bit anyway, not every dip will mean you're about to ovulate. It does take a few months to know what your own personal trend in temperature is as everyone can be different.
If you're charting with fertility friend then they have some very helpful charting lessons you can read through as they're really informative.
There's also a charting thread here and new people are always welcome. It's a great thread to learn more about charting and to ask questions and someone is bound to know the answer. That's how I learned everything.
Good Luck!