You have three concerns here.

First is what the university and your advisor will permit as valid for a dissertation. Your advisor is a good source for this.

Second is copyright. I suspect that you no longer own all of the rights to your work if it is published. One normally yields most rights to the publisher. What you can reuse is up to them, but many will be generous in this regard. But you probably need something in writing.

Third, and maybe most important, is the danger of self-plagiarism. This is governed by custom, not by laws, but your reputation depends on getting it right. The normal way to avoid self plagiarism is to treat your own early published work the same way you would treat the work of any other researcher. Quote from the early work and give proper citations. Just copying (without quoting) is what gets you in trouble here.

The reason for avoiding self plagiarism is a bit different from ordinary plagiarism. When someone reads a scientific or other scholarly work, it is often necessary to put the work in context. Researchers want the complete context of a work including whatever references and citations and background the earlier work implies. If you just copy without citation, then the context is denied unless, as in the case of a "stapled dissertation" the new work is just a collection of earlier papers.

There is one benefit here in your situation. You will probably, with the consent of your publisher and your advisor, be able to quote more extensively from your own work than would be permitted if you were quoting the work of another. Then it becomes a matter of presentation and formatting, making it clear what is old and what is new.

You have three concerns here.

First is what the university and your advisor will permit as valid for a dissertation. Your advisor is a good source for this.

Second is copyright. I suspect that you no longer own all of the rights to your work if it is published. One normally yields most rights to the publisher. What you can reuse is up to them, but many will be generous in this regard. But you probably need something in writing.

Third, and maybe most important, is the danger of self-plagiarism. This is governed by custom, not by laws, but your reputation depends on getting it right. The normal way to avoid self plagiarism is to treat your own early published work the same way you would treat the work of any other researcher. Quote from the early work and give proper citations. Just copying (without quoting) is what gets you in trouble here.

The reason for avoiding self plagiarism is a bit different from ordinary plagiarism. When someone reads a scientific or other scholarly work, it is often necessary to put the work in context. Researchers want the complete context of a work including whatever references and citations and background the earlier work implies. If you just copy without citation, then the context is denied unless, as in the case of a "stapled dissertation", the new work is just a collection of earlier papers.

There is one benefit here in your situation. You will probably, with the consent of your publisher and your advisor, be able to quote more extensively from your own work than would be permitted if you were quoting the work of another. Then it becomes a matter of presentation and formatting, making it clear what is old and what is new.