I am trying to follow the tutorial „Your first game“ here: http://docs.godotengine.org/en/latest/getting_started/step_by_step/your_first_game.html
I have created the project and unzipped the assets into my project folder. Now I try to create the sprite animation, as outlined here: http://docs.godotengine.org/en/latest/getting_started/step_by_step/your_first_game.html#sprite-animation
However, I can't „Drag the two images for each animation, named playerGreyup[1/2] and playerGreywalk[1/2], into the “Animation Frames” side of the panel“:
- Dragging the files from the explorer does nothing
- The files don't show up in the „file system“ pane on the left
So I tried to add the files by using the „load resource“ button, but I get:

On stdout I see:
ERROR: No loader found for resource: res://dodge_assets/art/playerGrey_up1.png
At: core\io\resource_loader.cpp:285
Do I need to convert the PNGs into a format that Godot understands first? If so, which format is this?