1) Install the WordPress plugin from here and activate them. Upon activation go to Settings-> Help Ninja
2) Go to Help Ninja Dashboard Manage -> Apps -> Easy Digital Downloads and click Add your store.
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3) Enter the store URL and then select the mailbox and click Add
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4) Once added copy the access token
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5) Paste the access token and click "Save Changes" on your WordPress site and that's it.
You should see the last five purchase details of a customer on the right side widget.