Hmm, I thought Red Hat had shipped E with 7.3, but looking at the package list I guess they didn't.
Are you using a graphical (runlevel 5) or CLI (runlevel 3) login?
If you are using runlevel 5 then you can use the GDM configuration tool to add E to the list of options. It will be listed under your system menu.
If you are using runlevel 3 then edit ~/.Xclients-default and run E from there. Just replace whatever is there now with:
You won't need the full path if the E executable is in your path already.