Hi,
Lindsays right with her advice. It's best to start soon after your period and use them every day until you get a positive, the first month you use them. You'll probably find that you ovulate around the same each month so the subsequent months you can start using them later - depending on when you ovulate.
If you only test every 4 days, then there's a good chance you'll miss the positive result. Once you have a positive result, you normally ovulate within 24-36 hours, this is the time that you need to be BD'ing.
Also if you are charting your temp, remember it's your waking temperature so you need to take it first thing before you get out of bed and preferrably at the same time each morning. Read the instructions carefully that come with it.
I charted my temps for the first time (the same month I got my BFP), I found it was a great insight into what's going on in your cycle.
Good luck with it all. OV sticks are great, helps you maximise your chances of conceiving.