Resizing bounding box without changing PNG size

Hello, I am very new to Adobe Animate. I was just wondering how I could change the bounding box size on my imported PNG's. I've went through various other posts in this community and still dont fully understand what im doing. First I just want to say I know I can resize the images in my drawing program, but Im trying to animate a character, and resizing and piecing it all back together wouldnt be ideal. Is there any way to just change the size of the bounding box? 

Heres the head bounding box size in Ibis paint, its the exact size of the layer:

Heres the head bounding box size in Adobe Animate, its the size of the canvas I exported it from:

What makes this worse is that every single layer has the exact same bounding box size, making it basically a nightmare if I wanted to animate it. Any help would go a long way.