Super, super easy! Chop up tomatoes, add some diced onion, add some finely diced peppers (adjust here to suit your taste, I like mild so I do bell, sweet banana, and just a little bit of jalepeno). Salt, pepper, cilantro if you have it. Eat fresh.
I also can it, same ingredients plus some vinegar and a little sugar. Cook it all together, put into hot, sterile jars, seal and hot water bath process.
Check out the extension web sites, they have good info for using your garden bounty.
Here is the U of I site, from here select "Tomatoes" then scroll down for fresh salsa recipe . . .
http://www.urbanext.uiuc.edu/veggies/
It's a great site for all sorts of information on vegetables.