As I know that most of online optical stores sell glasses not only with frames but also with the whole pair( frames and lenses in) ,so you don't need to take it to your opticians to put lenses in. You can have your eyes tested and get a prescription from your eye doctor, enter your prescripion online at the store you prefer, then they can start to process the eyeglasses prescribed with your prescription.
Online optical stores often sell the whole glasses including lenses and frames. There is no need for you to put lenses in at your optician. As long as you know your prescription, you can order the glasses online easily.