You can purchase a new license key in two ways.
Option 1 :
You can go to licensing tab of the installed plugin and click “Upgrade Now” button.
Option 2 :
If you don’t have plugin installed then you can follow the steps below.
1. Go to https://www.miniorange.com/pricing and select “Plugins” tab
2. Click on your plugin to open plugin pricing page
3. Click on “Upgrade Now” button