Your PhD or Masters thesis or maybe even your undergraduate dissertation can provide a great opportunity to get your research published. Depending on the length of your thesis and the research topics covered you may even get more than one publication out of your work. Publishing can help you further your career and can help with any future academic study that you may undertake. By publishing you are further disseminating the research you have done.
When turning your thesis into a journal article, you should avoid copying and pasting from your thesis. This would be considered self-plagiarism. You can reference your work and use direct quotes if necessary. Many journals will want you to disclose that your work is based off your thesis when submitting.
If you are currently undertaking a thesis, you should consider making your work available through your place of study's institutional repository. While this is different from having your work published as a journal article or book, it does make your work publicly available. Ask the library or your supervisor for details on how have your work added to your institutional repository.
Consider reaching out to your supervisor for advice if you are looking to publish your thesis. They may even be interested in co-publishing the piece with you and help get it ready for publication.
Journal articles require a consistent tense. Avoid including future tenses.
A thesis tends to have a broader focus than a research article. You typically would have more than one research question in your thesis but for an article you should narrow it down to one or two.
Journal articles are typically much shorter than a thesis. Each section should be much more concise. Go through your citations and trim down to the most relevant. Your methodology section should also be condensed especially if you are limiting it to just a part of your research. Similarly trim your results and discussion down to just the relevant information.