In order to enable EPG, you need to get to myth-setup on the master backend then look for EIT and enable it
(sorry for not being to precise but in remember that from the top of my head).
I had some occasions where i couldnt get EPG unless i import a channels.conf in mythtv then use minimal updates.
I have done a wiki DVB page so proceed to install as stated and EPG sould be enabled by default.
You can also use xmltv which apparently load about 2 weeks of EPG but i havent spent time on this yet
i as could not getting working from scratch from mythtv setup.
Hope this helps,