I have read lalalands post. Follow it and you will be fine, just practice. I like her idea of practicing on newspaper -- saves thread.
For me, I use my hands to guide the fabric as the machine pulls it through. The only thing I might add to lalalands post is to place a piece of tape the width of the seam that you want on the sewing bed (1/4 inch, 1/2 inch, whatever you are using). Measure from the needle to the right and place a piece of scotch tape, painters tape, whatever onto the sewing bed. Guide the fabric (newspaper) along the piece of tape. Don`t watch the needle, just guide the fabric along that line and keep the fabric along that tape line for a good 3 inches before it hits the needle. You will have a straight line.
If you need a manual, singer has a web site where you can download manuals for very old machines.
Good luck.
Aileen