If you get a bulge in the tire when inflating the tube then you have pinched the tube with the tire. This usually happens near the valve stem. The tube pushes the tire away from the rim, thus the bulge. It will then eventually cause a flat. To resolve this, once you have the tube in and the tire seated, push in on the valve stem. This will make sure the tube is fully inside the tire. Then inflate the rest of the way.