Well, are you 100% sure that the installation of the phpmyadmin contrib was succesful? First quit MC (press function key F10, confirm with Y). Then issue this command at the command line:
yum list installed smeserver-phpmyadmin
The output should be something like this:
Installed Packages
smeserver-phpmyadmin.noarch 2.11.1.2-0.dmay installed