You shop.  Amazon gives.

Amazon donates 0.5% of the price of your eligible AmazonSmile purchases to the charitable organization of your choice.

AmazonSmile is the same Amazon you already know. Same products, same prices, same service.  If you don't have an Amazon account the site will provide a way for you to create one.  If you already have an Amazon account sign in with the same user name and password you use at Amazon.
 
On your first visit, you'll be asked to select the charity you wish to support.  Select VerdeCares - remember there is no space between Verde and cares. 
 
Once selected, your charity is stored for all future visits, and smile.amazon will advise you on every visit the total of how much they have donated to VerdeCares on your behalf.  Once set up, remember to go to smile.amazon for all your Amazon shopping.