How do I play an animation upon mouse cliick

how long is your animation? is it 1 frame or more?

you can loop animations or not, no loop is all frames in the animation, loop is always repeat the animation

Also, this belongs in the Fusion 2.5 forum, not the Developer Services forum.

create the animation, put it in the sprite editor in game, set it for an animation you won't use for other things. for instance if you have it as a static object, set it for "Walking". If it's a character or something set it for "Disappearing" or something else that won't happen normally. On the direction options tab, check "Looping".
next

Always
(your object) : Stop animation (your object --> Animation --> Stop)

Repeat while left mouse-key is down
(your object) : change animation sequence to walking (your object --> animations --> change --> Animation sequence --> walking)

Hope that helps

Edit:
Sorry, that was a misunderstanding
change repeat to "when clicked". My bad.