Crutchfield has a pretty good, (but generic) guide located here:http://a248.e.akamai.net/pix.crutchf.../amp_guide.pdf
Basic Amp install goes something like this...
1) Power wire with fuse from + side of car battery to + on amp.
2) Short ground wire from - on amp into clean, solid metal bolt/screw into vehicle chassis.
3) RCA signal wire from radio output to amp inputs. In your case use the subwoofer or low pass (if available).
4) Speaker wire from amp outputs to speaker box inputs, wiring sequence may vary based on required ohm load, check amp manual!
5) Correct gain and crossover settings on amp dialed in. This may require some tuning by ear. Remember the gain control is not a volume level, its designed for matching the radio's output voltage to the amps input level. Turning it "up" will just increase noise and distortion.
The hardest part is normally routing all the wires thru the car since you have to find a hole in the firewall and make sure none of the wires get pinched or cut.
IMPORTANT: the fuse protects the CAR not the amp, so put it as close to the battery as possible. Keep in mind the power wire will draw plenty of current, thus it could cause the vehicle to catch fire if not installed properly!!! Do the ground wire first, then all other wires, once everything is locked down tight you add the fuse LAST.
And yes it looks like you missing the speaker wires that would go from the amp to the subs. You can grab some at any home improvement store, between 16-12 gauge will be fine.