For most users this process should happen automatically when you sign in to the application. If it does not you should be able to do so below. If you have any trouble, or have a licenses that was not obtained through the paypal store please contact email@example.com for help.
Locate your serial number
Open Sighthound Video, go to the Help menu and choose Show License Information
Your serial number is displayed near the top of the window
Add serial number
Log in to your account at https://www.sighthound.com/account/
Enter your serial number at the bottom of the page and select “Add”
From within Sighthound Video you can then select "Help->Show License Information...", click the license which now appears in the list and click "Activate" to begin using that license.