You first have to sign in to your Amazon account
Go to the coupon page and find the $3 off Venus Coupon (refresh as needed)
Coupon Page: http://www.amazon.com/Coupons-Grocery/b/ref=amb_link_85715391_1
Click on the coupon
Select this product
Gillette Venus Shaving Cartridges for Women, 8-Count Package: http://www.amazon.com/Gillette-Shaving-Cartridges-8-Count-Packa
Select Subscribe & Save
Your checkout page should look like this
Items: $16.35
Shipping & Handling: $0.00
Subscription Discount -$2.45
Your Coupon Savings -$3.00
Total Before Tax: $10.90
Estimated Tax: $0.00
Total: $10.90