Why do you need to peel peaches to can them

By far the easiest method is to use a pan of hot water and a bowl of ice water. Essentially, bring a pan of water (enough water to cover the peach to a boil. Meanwhile, with a sharp knife, make a small 'X' shaped incision in the top and bottom of each peach.

When the water is boiling gently place a few of the peaches into the water and simmer for around 20 seconds, just until the skin can be seen coming away. At this point use a slotted spoon to remove the fruit from the boiling water and place them in the ice water. After 20 or 30 seconds you should be able to remove the skin with your fingers.

The same technique is used with tomatoes

You cannot preserve just any salsa recipe (unless you're just freezing it).

Tomatoes are on the border between acidic and non-acidic foods. What this means is that they can be water-bath canned if they are sufficiently high in acid; but, if they are low in acid, they need to be pressure canned.

If you want to be sure to avoid trouble, follow a tested recipe. Salsa recipes will have a careful balance of low and high acid ingredients. Do not alter the proportion of acids (tomatoes and vinegar or lime/lemon juice) and low-acids (other vegetables, peppers, etc).

The recipe you choose should specify if it requires pressure canning or water-bath canning. One of those two methods must be used, though... you can't just put it in jars and save it.

For tested recipes, see the Ball Blue Book, the Ball website, or the National Center for Home Food Preservation.