Starting at the back of the fabric, push the needle and thread through at the point you would like the French Knot to sit
Wrap the thread around the needle once
Then place the needle close to the fabric at the entry point of the thread and wrap the thread around the needle a further two times
Keep the thread taut around the needle and begin to slide the needle out until the thread is sitting at the tip. Then push the needle into the fabric, close to the original point
Pull the needle and thread through to the back of the fabric. You just created a French Knot!