Basic questions regarding Trace Bitmap

Hello. This is a novice question so please be patient (i already checked the tutes on this site)

i am trying to do a trace on a photo, i want to empty the color of a person in the photo and fill the white space with color using a tween, like kind of “filling up” the persons shape. then i would like to replace the colored space with the original persons image.

i have been told to do a trace. which i did, but that took ages. my real problem was, once i have emptied the image of color, how do i return the overall photo to a bitmap ?

im simply trying to master what is done on this site

i have had people tell me today in such superior tones how “easy” this effect is, but they havent bothered to explain it.

if anyone has any tips for this i would really appreciate it thanks a lot.