If you are getting loops on the back, your top tension is too loose. You need to tighten your top tension. Turn your knob clockwise or toward a higher number.
Tension is a tug of war between the two threads.
Remember, fast foot, slow hands. It's a rhythm you have to get into. The tendency is to want to go as fast as your foot - resist the urge.
You might also try with your feed dogs up. Some machines are more particular than others, and what works for some doesn't necessarily work for all.
Good luck!
Ebony