See this help page for instructions how to add published or unpublished research to your ResearchGate profile: https://help.researchgate.net/hc/en-us/articles/14293005132305-How-to-add-research. However, uploading your master thesis to ResearchGate will not be regarded a publication because ResearchGate is neither a journal nor a publisher. (See also "Is ResearchGate a publisher?" in https://help.researchgate.net/hc/en-us/articles/14292596164753.) It would be better to write articles with the results of your work and to submit these to journals.

To publish your work on ResearchGate, you do not "publish" it in the journal sense, but rather add it to your profile, either by uploading the full-text file or by creating a publication record from an existing journal publication. Log in, click the "Add new" button on any page, select the publication type (e.g., "Published research," "Article," or "Preprint"), and then enter the details and upload your file if you have the rights to do so.