You definitely want to have sex when you are ovulating. You can get over the counter ovulation kits and a basal thermometer and the cervical mucus as well. On med help they a tracker to help you know when the best time to conceive is. Use the ovulation kit and basal thermometer first thing in the morning. I know what you are going through my husband and are have been found this sice last year but have been trying since we got married about 7-8 years ago. I hope this help good luck. :)
Women tend to ovulate mid cycle. So for example...if you have a 28 day cycle then you would most likely ovulate around day 14 but your fertile days would around days 11-16 adn that's the best time to be having sex.
Obviously this differs for each women, so if you want pin point ovulation then I would suggest using ovulation sticks.
If you don't want to go into all those yet, I would just have sex every other day from around days 10-20 of your cycle....that should cover all your bases.
When you are ovulating. Check your temperature as soon as you wake up. 98 degrees for at least three days. Good luck! Find more info about checking for ovulation at webmd.