How to make pngs into tilemap and sprites for unity

I have a tilemap in png form from Pyxel Edit I want to put in Unity. I tried to just use the png but I realized I can’t do that and am now stuck.

The backgrounds are not there because I used a decent software for the art but I have not got the foggiest clue as to how to make a tileset using the pngs. Unfortunately most of the replies here about pngs to tilesets are about Pygame which I am not using.

Here is an image of the tileset I made:

the tiles in question