After installing the plugin, you need to go to the license tab, enter the license key, and hit the Save & Activate button.

You can get a license key anytime by logging in to your account from here. https://xylusthemes.com/my-account/ 

Note:  Each purchase of this plugin entitles you to the plugin files plus one year of free support and updates. After a year, we’ll send you a reminder to renew your license at a 20% discount.

You can renew your license by clicking the Renew button and if you don’t want to renew, you can continue to use the plugin but support and updates will no longer be available.