You need to release the cable from the pedal cluster at the clevis pin. Then you can adjust the clevis that screws onto the cable. Best advice I got was to add some anti seize to the pin in case you need to remove it again.
http://forums.pelicanparts.com/porsche-911-technical-forum/825688-clutch-cable-replacement-question.html
My hands and head still hurt from banging them in such a tight space.
Good luck!