OK so first select you trace area and modify high pass, low pass and threshold to highlight everything you need. I am not going to go into a ton of detail on that as it would take about 20 photos. Tracing without Tears video does a good job. For this Photo I did a High pass of 3.7 Low Pass of 1 and Threshold of 48. Hit Trace.
It will look something like this with both lines over top of each other.
Next use the Weld function we learnt about earlier.
After you weld it will look like this one piece with and inner and outer lines. again Release your compound path then delete the outer one.