I’m still new to pixel art. let me show you how to make sprite has transparent background.
First open up your sprite on paint.net and click one the magic wand (i point it with black circle), next set the tolerance to 0% and set the flood mode to that pic (first you will see it has lamp icon, change it to world icon)
After you set that point the magic wand at the white background and click it, it will looks like that and then cut it.
Voila, you just removed the white background!
Do this to all items,sprites,paperdolls that has white background goodluck!