After you bought the license you must send an email to license@reportadd-on.com with the serial number you are buying the license for. Install the software on the computer you want to buy the license for. Install the software and open one of the excel file related to the customization. Open the Report Add-On menu and press the About button, a pop-up window will appear with the information as shown below. Copy the value of "Licensed to Serial Number" and paste in the email. Send the email with the same account you bought the license. You will soon receive a respond with the license file. 

The license is for one computer for 1 year.