In many cases you will no longer have to yummify a repository you mirror (where by ``yummify'' I mean prepare the repository so that yum clients can work their magic when updating or installing software from them). Yum is being widely adopted by the major RPM distributions so that a mirror of the Fedora repository given in this article will very likely already be yummified and will equally likely automatically install yum as a part of the base distribution. However, you need to know how to yummify a distribution, as you may want to set up your own repository of RPMs you've built or collected yourself, or you may need to re-yummify a repository after updating or adding RPMs to it.
This is, fortunately, extremely simple. Assuming that you've installed your repository on the primary path /var/www/fedora as in the running example, simply run:
$ yum-arch /var/www/fedoraThat's it. Yum-arch will descend into the fedora tree, looking for RPMs, extract their headers (with all the requisite dependency and path information) and structure it so that it can be delivered to any yum client without the need of downloading the RPMs themselves. It is possible to have more than one RPM directory in the repository; all RPMS in the tree will be yum-accessible. However, it is not possible to mix architectures, and is a generally bad idea to even mix RPMs built for different revisions.
Note that there are a fair number of options that yum-arch recognizes, most of which aren't terribly important for beginners to be aware of. The one possible exception is -c, which causes yum-arch to check GPG and/or MD5 checksums, if it can. Otherwise you should (as always) read the man page and other documentation before experimenting with options.