How to make link on pressbooks.pub?

Hello Everyone,
While searching some ecomm product i found a new website which is on rank.
ubalt.pressbooks.pub/technologyblog/chapter/fungabeam/
pressbooks.cuny.edu/techblog/chapter/yooje-360-toothbrush-reviews/
Please guys help me how to generatebacklink on that website.
Any help will really appreciate
Thanks

Those are Pressbooks subdomains, usually user-generated or academic content you don’t ‘build links’ there, you need legit access or contribute content naturally.