Need help on adding an Unsubscribe Page

I there any source I can download readymade templates for unsubscribe page and add it to my website.
like www.mysite.com/unsubscribe

I have downloaded a template from codepen.io, but I am unable to add it to my website. Is there any source where I can download and add it to my site directly.

Can someone guide me on this?

You can buy the template on themeforest but anyway you will need to code the backend part that delete the user from a database with all the user who have registered for the newsellet let's say for example.

You can code the backend in PHP and if you're familiar with javascript there is also node.js