I'm rather new to the home theatre audio setup, so right now I'm in the process of setting up my first receiver + speakers.

The speakers are as I have expected, cutting and removing the insulation from speaker wire then connecting to the receiver. However, I never realized the subwoofer differs from the speakers and does not use speaker wire.

My question is, what exactly does a subwoofer use to connect to a receiver? My sub is essentially an Energy ESW-8, so this is how the back looks.
http://www.audioholics.com/reviews/speakers/satellite/energy-take-classic-review/DSC_0124.jpg/image

Apparently you need a subwoofer wire? I have looked around and some say it is just a digital coaxial cable? Can someone confirm this? Also, does it matter if you only use one of the two connectors on the subwoofer? Thanks.

1 in is fine
mono sub cable

It looks like you have it connected correctly. However, if you're using the Bass Management in your receiver/pre/pro, turn the low pass filter all the way up to it's highest setting. In your picture, it looks to be set at 40 Hz, in which case you'll only get bass below 40 Hz.

Craig