You have to wire the voice coils of the sub in parallel. To do this, connect both + on the voice coil to eachother and connect both - on the voice coil together. Now connect one of the + on the sub to the + on the amp. Then one of the - on the sub to the - on the amp. This will get you 1 ohm.
shorty is right, use 2 gauge. It is safer and will give you room for another amp later.
Run RCA cables from your head unit to your amp through the car on one side. Now connect a remote wire to the remote lead on the HU and run this with the RCAs. 18 gauge is fine for this. Just be careful not to pinch it. The remote wire might be included with the RCAs, depending on the RCAs you buy.
On the other side, run a power cable from your battery, through the firewall, to the trunk. Use a ring terminal on the end of the wire to connect it to the battery post. Get a fuse holder and a fuse (200 amps max for 2 gauge wire). This goes on the power wire between 6 and 18 inches from the battery. Careful when hooking the ends of the wire to it to make sure it's all sealed so you don't short it out. Use heat shrink, electrical tape, or liquid elec. tape.
Connect the power wire to the power on the amp. Now connect a 2 gauge ground wire from your amp to a solid metal surface as close to the amp as you can. Use a dremel and sandpaper and grind away all the paint on the surface to ensure a metal to metal contact. Use a ring terminal and a self tapping screw and washer to secure the end of the wire to the metal.
Connect the remote wire and the RCAs you ran to the remote on the amp.
Secure your amp! Screw it to a piece of carpeted MDF or even chipboard. Screw this piece of wood to the trunk of the floor or the back of your seat. IF YOU SCREW THROUGH THE FLOOR OF THE TRUNK, DON'T GO INTO YOUR GAS TANK ACCIDENTILY.
Hopefully I didn't miss anything too important...if you have any specific questions do a search first then go ahead and ask if you can't find anything. Good luck with the installation, it's a big learning experience so don't get frustrated.