See this help page for instructions how to add published or unpublished research to ResearchGate: https://help.researchgate.net/hc/en-us/articles/14293005132305-How-to-add-research. This includes also theses. Click on "Add new" and select "Published research", then "Thesis". But note that this is not a "publication" in the narrow sense. You will just make your thesis publicly available. See also these discussions on a real publication of theses in the form of papers or books:

https://www.researchgate.net/post/I_have_submitted_my_thesis_the_question_is_can_I_published_the_chapter_of_my_theis_in_any_journal/1

https://www.researchgate.net/post/Publishing-your-thesis-as-a-book-and-also-publish-journal-articles/1

https://www.researchgate.net/post/How-to-turn-a-dissertation-into-a-book/1

https://www.researchgate.net/post/How_does_a_thesis_convert_into_a_book/1

https://www.researchgate.net/post/Which_is_the_best_publisher_to_publish_the_PhD_thesis/1

https://www.researchgate.net/post/I_want_to_publish_my_thesis_as_a_book_What_authentic_publishing_houses_do_you_recommend/1

https://www.researchgate.net/post/Who_can_provide_information_on_available_free_of_charge_academic_book_publishers_where_I_can_publish_my_dissertation/1

You can publish the most important and interesting excerpts from your dissertation either on researchgate.net or on academia.edu and other similar resources.

First, you must clarify what kind of "Publishing", you are looking Zaal Anjaparidze provided platforms where you can "socialize" key concepts of your Research as a summary from your report (The Dissertation). However,it might not be the type of publication you are looking for.

Generally, dissertations are not published by anyone, while they may be informative new profound BoK, they are lengthy reports read by you, more times than the number of people, who actually read it. Basically, they are works of a student, demonstrating their readiness to teach or practice, a driver's license in your field. Though you should be proud of completing the report of your "training", you will have know what type of publishing you are looking for, Below I have summarized some of the types of publishers:

1. Academic Publishers.

1.1 Peer Reviewed Journal: Articles undergo rigorous review, and must be original work, if dissertation, must be summarized to a few pages in a format as required by publishing entity.

1.2. Conference Proceeding: Part of collection of papers, presented at a conference.

1.3Theses and Dissertation: Often Availaible in Institutional Repositories, Or Worldwide repository supported by ProQuest network.

1.4 Books:Scholarly books. Published by Universities an Academic book publishers.

1.5 Reports and Working papers: usually as preliminary papers from institutions and professional associations.

2.0 General Publication.

2.1 Magazines and Newspapers; general audience.

2.2 Blogs and Online Articles: Informal Articles covering a broad range of artices from Fake Blogs and Online Articles: Informal Articles covering a broad range of articles from Fake News to Factual news.