Yum has been distributed with Fedora now.
Yes, you can use yum to update to the test version of FC2.. but FC2 itself is not yet released. In updating by yum you will have some problems to deal with individually: this is not the best method. Instead you should download the test 2 cds and install as a 'upgrade', you will have a much better upgrade experience in doing so.
There is an article online about updating with apt at http://fedoranews.org/ghenry/apt-fc2/
, the same procedure would be followed for yum (using the correct yum config syntax of course).
I have to mention that because the latest is a test version there are many known bugs... do not update to FC2test2 unless you are prepared to deal with them. Do your research first and take a look at the issues being raised on the fedora-test mailing list (searchable archives available at fedora.redhat.com, see the participate / communicate section).