The amazon capsule is a section designed specifically for amazon ads and items placement. When you are creating a hub or under the edit mode of your hub you will see a box in the top right that says "ADD MORE CAPSULES". Click on the amazon capsule and by default it will be placed on the bottom of your hub. You can move it around with the green UP/Down arrows to get it placed where you want it. Goto the Amazon capsule and click edit then from there you can choose specific products or keywords. Then save your hub and you have successfully added the capsule.