If you boot straight to X then running pure enlightenment requires more tinkering with /etc/X11/xdm/Xsession and it requires you to put a file into /etc/X11/gdm/Sessions called Enlightenment with following contents
now go to /etc/X11/xdm and edit file Xsession, you'll see a case statement so just add the following entries to that case statement
next time you login you'll have Enlightenment entry in the pull down menu of GDM.
If you use KDM (defaults to KDE) then the steps are a bit different
You shoud add enlightenment into the list of SessionTypes in kdmrc file. To find that file use find
find / -name kdmrc -type f -print
and edit /etc/X11/xdm/Xsessio file as described above