How can I manually add outlines to image traced using Image Trace

I have an image traced in Black and White mode using Image Trace in Adobe Illustrator. Doing this gives me outlines of which areas of the image will be rendered in white and which will be in black. I know I can adjust the outlines by increasing/reducing the Threshold in the Image Trace window but I want to find out if I can/how to do this manually.

Thanks.