In 2008 when we first tried and actually succeeded in having a small garden, I made fresh salsa a couple of times. I thought the flavors were best when roasting the veggies (tomatoes, peppers, garlic--whole cloves) in the oven first--grill skillet with oven proof handle, olive oil and bake at 375-400 until the skins are starting to char. Peel and seed (or not) and put all ingredients in food processor. You can use as many peppers as you want.
The seeds really add heat so leave them out if you don't want it as hot.
Also, I used fresh cilantro, fresh squeezed lime juice and salt.
Sorry I can't help you with the canning although I would think you could can it just like any other veggie in a pressure canner.
Good luck!