You can use an existing repository definition in /etc/yum.repos.d. The definitions in this directory look complicated, but the only changes you need to make are in the names, base URLs, and GPG keys, all of which you can crib from looking at the repository that you are adding in your Web browser.To make things simpler, you could set the gpgcheck field to to turn off the use of the GPG key, but for security's sake, you should avoid that course.
During the upgrade you can use a free driver instead, since an upgrade hardly requires 3-D graphics.
As a final preliminary, if you have SELinux enabled, turn it to permissive mode, so that it does not react to attempts to change configuration files.
This method avoids the long preliminary download of an ISO image, but it forces you either to upgrade at the peak period for use of the newest repository, or, if you wait too long, to perform the extra step of hunting down the necessary version of fedora-release.
In other words, delay too long and the main advantage of this method is lost.
Add the new repositories, reboot, and you will be ready to upgrade. In this command, the release number is simply the number of the release.