Built in method

Inside the External folder of the game you’ll find many things but at the very bottom you’ll see the XNA Content Builder.exe.

It will convert every png in the “Content/Units”, “Content/Maps/Tilesets”, “Content/Animations/Sprite Sheets” and “Content/Animations/Sprites” folders automatically once launched. No need to move files or anything.

If you want to convert images from a different folder, you can add it into the External/XNA Folders to convert.txt file.

If everything fail you can use tConvert which is much more robust and supported.