Depending on how long your cycle is will be the best time to test using an ovulation predictor kit (opk).

In most women, ovulation occurs approximately 14 days before the start of your next mestrual period. Therefore, if your cycle is normally 28 days, start using the opk around cycle day 11 and continue until they run out (most kits have at least 5 test strips, so this would cover cycle days 11-16). If your cycles run about 35 days, you would begin testing around cycle day 18 (5 tests would then get you up to about cycle day 23, if your luteal phase - or the time between ovulation & the start of your next cycle - is 14 days then you could expect to ovulate around cycle day 21)

charting your basal body temperature (bbt) can be helpful in determining a pattern so in following months you will be able to see the best time to test, but one chart on its own is not really going to show you when to test. By the time you see a sustained temperature rise that indicates ovulation, the egg would already have been released and the lutenising hormone (lh) surge will not be able to be detected using an opk

hope this helps!

Fiona