First, you should choose the usage of your glasses (for reading). Second, enter your PD.(near PD if it was giving in your prescription, if not, near PD is commonly 2-3mm less than the far PD). Third,enter the SPH power respectively for your right eye and left eye. The value is usually showed as a positive number, for example: "+3.00" .Fourth, enter the ADD power. ADD means near additon which is used for making single vision reading glasses, computer glasses, bifocal & progressive eyeglasses. Some eyewearers may find their ADD values are put under the ''N.V." on their prescription.You can enter the same ADD for OD and OS if you have only one ADD value.Hope this help.