Hello Axel,
Apologies for the delay in getting back to you. We had a major cyclone in our city and I have difficulty getting good internet connection for the past couple of days.
Looks like you have only installed the base plugin and have not installed the add-on.
In the receipt email (which I have resent again), you will find a link to download the add-on. Instructions to install the add-on can be found at http://bulkwp.com/docs/installing-addon/
Please follow the instructions to install the add-on and once the add-on is installed and activated, you should be able to find the field where you can enter the license key.