Making a running animation

I want to give a running animation to my character I made that ONLY animates when walking in either direction. If someone could please help me that would be awesome. Heres a link to my game, because why not? :

keyboard{key used to move}-down ----- start-Animation(loop)
same keyboard-up ----- stop-Animation

You should experiment a few minutes before asking on the forums, because logic like this should be pretty simple. Please refer to the help page or the guides/videos before asking for help.

aahhhh, thanks

I would also like to say, that I overlook really simple things