1. Go to
www.smile.amazon.com
2. Make sure you're signed in to your account
3. Search for Just People, Inc.
4. Make sure you select the correct JP! It should say Norcross, GA.
And that's all! Remember, to participate you have to shop using Amazon Smile. Unfortunately this does not work in the regular Amazon site.
This also works in the app - but you have to enable it separately! Just go to your settings within the Amazon app and turn Amazon Smile on.