After obtaining a Sail Premium license key, add it to your Sail CLI client configuration:
sail config premium <license key>
Make sure you also have an e-mail address configured with Sail:
sail config email <e-mail address>
Note that with a premium key set, all new Sail applications will be premium-enabled by default. However, if you wish to enable premium for an existing Sail application you can use the following command:
sail premium enable
Note that Sail Premium creates a new SSH key and authorizes it on your server, while sending the private key to the Sail API. This key is used for Sail API to access your server on your behalf for health checks, backups and more.
Enabling premium will also update your server configuration files, in particular Nginx configs, so if you have made any customizations in these files, make sure to back them up before enabling premium.
If you have any questions about Sail Premium, feel free to get in touch.