Welcome to the QB first of all and as you can see there are many people here that will help guide you through the learning process. All of us have been where you are. Learning to guide our fabrics through the machine and get the seam allowance that we want is a challenge. When quilting a 1/4" seam allowance is a difficult achievement and takes a great deal of practice. After 30+ years I can still struggle with a good straight seam allowance, especially as I change from one machine to another. Pressure foot and needle placements can vary a great deal from one machine to another. Practice, practice, practice is what is going to help you the most. Go slowly and keep your attention on you guide marking. I use my outside side of the pressure foot as my guide and align the needle for the right distance. This works well for me but you may find something else that works perfect for you. Getting it straight will come in time.