I need some help.

I have here these questions three...err, two.
One...how do I activate THX Surround EX on the receiver? Can't for the life of me figure it out. So I can get the 6th channel active on DD EX DVDs.
Two...how do I matrix out 5.1 movies to include the 6th (rear) channel? So I can improve my soundstage?
I've been lookin gover the manual for a bit now:
http://us.marantz.com/DFU_SR7002_SR8002_final_eng.pdf
...and I just can't figure it out! Anybody have any ideas? Thanks in advance...