It's pretty easy. I bought 10 ft of 8 gauge stranded copper wire, at Home Depot, some crimp on ring connectors at Orchard Supply, and an ANL fuse holder and a 70 amp fuse on Amazon.
I replaced the small nut that holds the existing wires in place on the alternator with one that wasn't rusted...used a stainless nut and lock washer with some anti-seize to keep it nice.
You should always start running the wire from the alternator and don't install the fuse until everything is connected. You don't want to be trimming, stripping and crimping a live wire. I know that's obvious sounding but when I started the job I almost did it from the battery out to the alternator so maybe it's worth mentioning here.
I ran the wire from the alternator over to the drivers side fender, attached it with a couple of zip ties to the existing harness, then thru the front of the support near the LH headlight. Then I strung it under the front brace in front of the radiator. Attached the fuse holder to the same support next to the battery, leaving room to get to the terminals. I use a metric Nutsert to attach the holder. Then it's a short wire run to the positive side of the battery. Used weatherproof heatshrink on all the crimped connectors. I also used some heatshrink to the wire where it passes thru the brace to reinforce it against abrasion.
If I can remember how I'll post a couple of pics.
It's a pretty easy mod and the difference is obvious. My voltmeter moved from hovering around the 12v mark with the headlights on to about 14v. I also wire brushed the rust and corrosion off of the alternator terminal which probably helped as well. The only other thing is to remember to attach the shorter wire to the fuse holder before you attach it to the battery. You don't want a live wire moving around when you're attaching it.