Selecting Colors

So let’s say I imported a .png that says to have a transparent background. When I import this, the background is black. This would not be a problem if I were able to select the black only (which, keep in mind, is on the same layer as everything in the imported picture) with something such as the magic wand tool. Is there something I can do to make the backgrounds on pngs I import truly transparent, or select and delete a single color from an entire layer? Thank you! I attached an example.

Did you confirm the image really has transparency, for instance in Photophop? If you import it as Toon Boom Bitmap Drawing it should have transparent background. You can use a Blending node set to Screen to remove black or Multiply to remove white. You can also try the Chroma-Keying node.

Yes be sure it is truly transparent with any image editing software.
How is it when rendered ?
You can try modify the transparency mode in layer properties/ drawing to “premult with black” or "straight ".