Convert Photoshop Elements 2018 from trial to licensed

I have been trying out the trial version of Photoshop Elements 2018 and decided to purchase it. Now that I have a license key I would like to enter it. I would have thought that it would have been relatively easy to enter the key. But after much searching through every screen, option and numerous forum posts, I am unable to get to any screen where I could enter the key. On a Mac, how do I navigate to a screen to enter the license key? Or do I need to uninstall and reinstall the software.