how to install midnight commander

As I can see "mc" is present in CentOS 4.x repository, so you can use yum to install it:

yum -y install mc

another thing: where should I upload joomla?

I want to install joomla, so I want to connect by ssh. download using wget and untar the file. I have connected ssh´ed with putty, but where are the directories of my domains?