Please help me out.

I had the Onkyo reciever TX-SR601 where it only have 1 Pre-out for Sub. I just purchase a Klipsch 10" Reference Sub and its instruction describe about connection with speaker cable or LFE. To connect to Pre-out, the Sub has Left and right RCA input but the receiver has only one Pre-out. My few questions are:

1. What is LFE (Sorry, I couldn't find what it means)?
2. How shoule I connect?
3. With my Athena speakers with two large front, I would like to know the best way to set up. However rest assure, I will experiment every way.

I am trying to set them up right now, so don't be lazy, get up and help me right away. :) Thank you very much

1) Low Frequency Effects. This is the .1 channel in 5.1.
2) Connect the pre-out to either the left or right line level (or LFE) input.
3) In your AVR, set all speakers to small, sub to yes/on, crossover starting at 80 and adjust to taste. Set the crossover on the sub to defeat or to its highest setting.

Thank You very much