You have a few options here:
1. Cheapest and least durable - clean it up real nice, squirt some grease in there and duct tape it together.
2. Durable but messy and takes about an hour of your time - buy a CV boot kit from your favorite auto parts store. The grease they give you for it usually sucks, I'd spring for a better quality grease than whatever comes with your new boot. Make sure you look into the boot stretch mod.
3. Best option but pricey - replace the CV axle with a new one or rebuilt OEM one.
There are lots of writeups for tackling the torn boot issue.
Have fun!