The app offers 2 days for trial so you should buy a license after that.
To make the purchase you can see this link: https://support.iSpyoo.com/hc/en-us/articles/115003117313-How-to-purchase-a-iSpyoo-package-
If you have 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.