This is how to take a .png file and use the trace function to create a line drawing.
Choose your .png file and add it to your canvas.
Select your image. Go to tools. Go to Trace Image.
Choose your settings.
When trace is finished, move your tracing off of the original. If it is set to a fill layer, change it to line.
Ungroup your trace and delete any extra parts that you don't want. Like the box outline.
Select all of the design and regroup your parts.