The manual won't say anything about it.
You have to get the RCA to mini RCA Y adapter, Radio Shack, or some other crappy electronics store has them. Plug your red/white RCA cable into one end and the mini RCA into the Mini RCA on the back and then select direct input with DP2 movie mode and wa la sorround sound. I also run an optical connection from my DVD player for movies, works awesome. Its a pretty tight little system and has bass to spare, I actually turn my Bass right down as I live in an apartment condo *sigh*.
Anyways, enjoy.