After you've purchased Grow Social Pro, you'll want to input your license key into the plugin. Here's how you do that:
You can find your Grow Social Pro license key by logging into the Mediavine Marketplace > Account > Account Details > Licenses:
1 - Head to WordPress > Grow > Settings > General Settings > Register Version (all the way at the bottom):
2 - Input the license key you received with your purchase of Grow Social Pro.
3 - Click Save Changes and you're all set!