Here is what it should look like. Don't worry about being able to see these stitches because you are going to rip them out later once your ruffle is sewn to your main piece.
Find your bottom thread and carefully tug, using your hands to pull the fabric towards the center, to create the ruffle.
Use a pin to secure one end, and then work from the opposite end to continue making the gathers till you get to your desired length. Make it look as even as possible. Tie a knot with the threads at either end and cut off the excess thread.