In order to cut out the png. file you would first need to create a vector ‘cut line’ (stroke - no fill) around the image in Inkscape, save it as an SVG, then upload it to the GFUI. I’ve read various things about Inkscape’s SVGs being in some odd type of format that gives problems when uploading. I don’t personally use Inkscape, but I’m sure someone on here who does will chime in with some help for you. Best of luck and welcome to the forum.
*edit; here is a link describing how to save an SVG properly in several different software apps. If you scroll down, you can review the procedure for doing that in Inkscape.