To help you find your fertile days (they can be different each cycle) most ladies use an ovulation predictor kit (OPK) that you can purchase from a drug store or a BBT (basil body tempature chart) that you can download online for free. Make sure to follow the directions on the method you choose.
Good luck!
fertile window happens 14 days after the first day of your period for most women. Sperm can live for 3 days so fertile window is the days leading up to the 14 days.