On the main Fedora Project website, under the section "Using Fedora,"
the tutorial for agave (at
http://fedoraproject.org/en/using/tutorials/agave.html ) contains
outdated instructions.
The website says to "Open up the Add/Remove Software wizard by selecting
the System → Administration → Add/Remove Software desktop menu item."
GNOME 3 has no such menus. The desired application is now launched
through Applications → System Tools → Add/Remove Software.