In general, it should take two to three weeks to properly break in your new running shoes. Loosen your pair first by walking around your house in them for several days to allow your foot to adjust. If you're anxious to get started, you can quicken up this process by wearing two pairs of socks (or one pair of really thick socks) with your new running shoes and then wear them around the house for a few days. Do not immediately put them on and start running, you'll get so many blisters!!!