Script jQuery Cookie Consent (or another type of script) in my owncloud

Good morning dear friends.
I contact with you as I want to incorporate my owncloud, to comply with GDPR, this script copied from ‘’:

I have entered it in between the <head> … </ head> tags of the files layout.base.php, layout.guest.php, layout.user.php (\ core \ templates ) but it does not work for me. Which file I have to modify to be able to introduce that script (or others) and run it in my owncloud?. I also tried to enter a <p> / <h1> tag to see if it was shown. Neither was successful. I would ask you, please, to help me solve this problem. Thanks for your attention. Best regards.