You can either buy a commercial tanning product or brain tan the hide like the native americans did. If you buy a tanning agent, then just follow the directions on the bottle. I've used "trapper's hide tanning formula" and it worked very well.

If you want to brain tan it you have to buy a tub of hog brains from the grocery store, Ingle's normally has it.

Scrape all the salt off the hide, it should be smooth when you're done. Just use a sharp knife and hold the edge at a 90 dregree angle from the hide and scrape. Then take a 5 gallon buckett half full of warm water and mush the hog brains around in it until its mixed up in the water. Then soak the hide in it for an hour or two. Next take the hide out and work it back an fourth over something, wring it out, streach it and anything else you can think of to keep the hide moving until it's dry. It takes a few hours for it to dry. Once it's dry it should be soft.

If you want to give the hide some color, set it over the smoke of a fire. Not the heat, just the smoke. That will also make the hide water resistant.