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.
3) Enter the store URL and then select the mailbox and click Add
4) Once added copy the access token
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.