Visit the LensKart website and add the products (sunglasses, eyeglasses, lenses, etc. ) you want to buy. Proceed to checkout when you are done. Now copy the promo code you want to apply to your clipboard. Paste this code during checkout and look for the price alteration. Continue with your payment information. Note that, not all the codes can be applied to all kinds of orders. So, make sure you go through their terms and conditions before applying.