Jer,
     I'm at work so I'll try to make this brief.  The easiest way to 
install a car audio amplifier is with the help of an amplifier 
installation kit.  This includes all the cables and usually some form of 
instructions.
     Just in case you don't get instructions here are some of the 
important things about amplifier installation;

1. You must get power to the amp.
2. You must ground the amp.
3. You must provide the amp with a signal.
4. You must turn the amp on.
5. You must secure the amp in the car.

1. The right way to do this is to run a large guage power wire from the 
battery to the amp.  By large I mean 12 guage or larger if you're hooking 
this amp to subs (they like lotsa power).  This wire must have a fuse 
inline between the battery and the amp, preferably within 18" of the 
battery.  This protects your car's electrical system from the amp 
shorting out and protects against a possible fire.

2. The right way to do this is to run the same guage wire you used 
for power from the ground terminal on the amp right to the chasis of the 
car.  Be sure it's contacting bare metal.  Scrape away the paint with 
sandpaper, put a ring connector on the end of the ground wire and paint 
the whole thing with clear (or antoher color if you prefer) fingernail 
polish to help prevent rust.

3. There are two main types of signal wires used in car audio, high level 
and low level.  High level are the wires coming out of your source 
(cassette deck or CD player) that you hook directly to the speaker(s).  
Fewer and fewer amplifiers have connections for high level lines, but if 
that's all you've got coming out of your source, you have to get an amp 
with high level inputs or get a high to low level converter.  Low level 
lines have RCA type connectors that plug into the back of your source and 
into the amp.  These are much better than high level lines and are much 
simpler to do the instal with. :)

4. There should be a little blue wire coming out of your source.  It may 
be marked "remote" or "power antenna" or something else, but most of the 
time it is blue.  This is usually refered to as a "turn on lead".  This 
is to be connected to your amp so that your source can turn the amp on.  
This can also be done with a switch, but that can be a hassle and 
dangerous if you leave your amp on all the time.

5. Lastly you must secure your amp.  This is very important and you 
should be ashamed of yourself if you just let the amp roll around in the 
trunk.  Ashamed because it's sloppy workmanship and dangerous.  In most 
cases you'll have to drill holes where you want to mount your amp.  (A 
good place is under a seat.)  You may damage the amp or something else if 
you just put the amp in it's place and start drilling through it's 
mounting holes.  The Easiest way to avoid this is to make a template.  
Take a piece of cardboard larger than the amp and put the amp on top of 
it.  Trace around the "footprint" of the amp and inside the holes where 
the screws go.  Cut out the outline of the amp and punch out the circles 
where the mounting screws go, a paper punch works great.  If you can, use 
your template to draw marks for drilling, but if that's not possible like 
say you have black carpet and a black pen, DOH!, you can just drill 
through the templates holes without risk of damaging the amp.

Make all your connections clean and tight and use crimp connections if 
at all possible, secure the amp correctly and whalla, major tunes dude!

Good luck,
Victor Albert