All you have to do is use the smile.amazon.com URL when making a purchase and make sure you have Asmbly set as your charity (more details about the program here).
It’s the only scenario where it’s actually cool to tell someone to smile more (when they are using Amazon that is).
Because Amazon doesn’t make enough money Thanks for the link @JohnWickham! Good thing I’m reaching out to them now to find out how we actually receive smile donations. I’m not sure we’ve ever actually received anything (although I can personally attest to funds being generated).