All you have to do is place the sprites (png) of the character you want to add and also the .XML file of the same character and you join the parts (Right, Left, Up and down, which are the movements of the character), then They are aligning the left part of the character’s foot at the white point in the center of the screen, and if the character comes out looking to the left you can press the button above to flip the character for more comfort when aligning it.