What to fill in the following gap in a journal's publication system: "The author was supported by ..."
This question asks what the author's funding is - in the case of PhD students, where the funding for your stipend/research is coming from. If your advisor has a grant that is covering your work, then the agency that issued the funding is the one you acknowledge here. If you have a scholarship, then the agency that issued the scholarship is the one you acknowledge. If you are self-funded, then you can leave it blank, or name your university.
In any case, if you are unsure, ask your advisor.