In the FIBA 3x3 player directory, your hometown should be the city in which you currently live. If you move to another city, you should update the city to your latest location.
In other words, it is not the city in which you were born, raised or went to school.
Having the correct city information is important, because then your profile becomes more easily visible to the local event organizers and basketball federations, and, further, your contribution to the growth of FIBA 3x3 is mapped correctly to the right geographical area. For clarity, nationality based-ranking that lists players holding a certain passport, independent of where they live, is a different thing than a country-ranking. You can read more about how to see country and nationality rankings here.