The SFML formula is current relatively basic. (More on that
here and then follow the links if you're really curious.)
ATM, it only provides header files + dylibs. No template for Xcode, no frameworks. If you don't care about the templates (that is, you can create an application bundle project for C++ on your own) or Xcode at all, then that's not a big deal: just add the dylibs manually to your project like you would add any framework. Unless your IDE is really dumb it should work. If you're using other tools, then you'll need to read their doc I guess.
If you want to use the template, uninstall the formula and install SFML as described in the getting started tutorial.