Go to your Cookie-Script.com account and copy your cookie-script code.
Log in to your Joomla Admin Dashboard.
Tap on the Template Manager.
Select the Styles tab.
Find the [Active template name] - Default file, and click on it.
Tap on the Custom code.
Paste copied Cookie-Script snippet into Before </head> section.
Tap Save & Close button.
Cookie-Script is installed on Joomla now and should be ready for use.