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After logging in, hover over the "Applications" tab
Select "Marketplace"
On the left hand side, select the merchant name to expand the menu
Expand "Stores"
Expand the store you would like to review reports for
Select the "Refunds" link
Once there, enter the Order Number and select Run Search
the “transaction number” in the Payment received Activity in Slate
is the Payment Gateway Reference Number 
Select "Refund" next to the order
Select the person whom the full or partial refund should go to
Update New Quantity Return to 1 for each refunded item
Enter the refund dollar amount
Enter comments in Refund Reason
Select Process Refund
I used the e-mail address to find the transaction I was looking for and that seemed to work fine.
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