The app offers 2 days for trial, so you should buy a license after that.
To make the purchase, you can see this link:
All checkout links here:
If you want to make the purchase with Paypal, please send an email to firstname.lastname@example.org
After successful payment, you will receive a license code, you can log in at Cpanel and then click Renew now button. It will show the link:
I have a gift code/license key.
Copy-paste the license code to textbox License Code ad the click Apply button. The expired date will be extended, which means you have activated the license.