How do I make an endless sprite animation

I have a sprite with 4 frames animation and I want that this animation doesn't end...how can I do that?

when you open animation editor and select animation then you can see one option "Loop" in project properties and set that loop to 'yes' .

when you open animation editor and select animation then you can see one option "Loop" in project properties and set that loop to 'yes' .

thanks!!!!