Do:

• ssh -X user@hostname firefox -no-remote

As a side note, you have done a minimal install of CentOS,  and you try the above and get the following warning “(firefox:2740): Pango-WARNING **: failed to choose a font….”, well you need install Firefox and and few other things.

• yum groupinstall “X Window System”
• xorg-x11-fonts-Type1.noarch
• yum install firefox

Now run ssh -X user@hostname firefox -no-remote and you should be good