You really should be able to fit a quilt sandwich under your walking foot easily by raising the foot lever. It might be a little snug once you lower the lever, but once you start sewing (quilting) it should move/feed the sandwich without any pushing, pulling, etc. If it doesn't you probably don't have the right foot.
Don't get frustrated though. Chances are they make a compatible walking foot for your machine. You may have to invest a little more money, but maybe you can get a refund for the other walking foot? Quilting with a walking foot is relatively easy. The walking foot feeds the quilt sandwich through automatically. Don't forget to adjust your stitch length to something a bit longer. It will be so easy once you get the right walking foot. Good luck! You'll get it and be quilting up a storm in no time.