In order to donate a portion of your sales on an item on Ebay to Aura Fury you must check the "donate a portion to charity" box when listing your item on ebay.
Next choose the percentage you wish to donate and select Aura Fury from the drop down list for which charity to donate to.
Ebay will discount your seller fees by the same percentage you donate to Aura Fury. So if you donate 100%, there will be no seller fees. If you do 50%, then there will be a 50% reduction to your seller fee. By donating you also get featured and denoted by Ebay for it. To find out more from Ebay on how to donate to charity click here.