How do you create a Tile map by importing a .png file?

I'm currently trying to import a texture in my tile map, by importing a .png file. However, it looks like I need a .xml or .tres file. If this is needed how can I convert my .png file to .xml or a .tres file? Do I need a different software for this task? Please let me know, and forgive me for some mistakes I made in answering this question, as I'm a newbie