How can I draw the outline for the object, which is detected object in a bounding box using Point Feature Matching?

I have the sample code, which is called Object detection in a Clutered Scene using Point Feature Matching:

(https://ch.mathworks.com/help/vision/ug/object-detection-in-a-cluttered-scene-using-point-feature-matching.html)

In this code, there is 2 object, the elephant and the box, both detected from a cluttered scene and they are in a bounding box. I want to draw the exact outline or change the color for these detected objects. I found, that it can be done with Region Growing algorithm, but I dont know, how to implement this in to the sample code. (i'm new for the matlab). How can I done it easily?

There is an example, how i want to select the object.