Hello, those forums are english only, so please, post at least a google translation with any message you post.
What exactly do you mean by "change its appearance" ?
I assume you would like to change the animation or the animation frame that the sprite is displaying, right ?
You can use the Mouse or Touch plugin to handle your click.
Using the condition "On object clicked", where your object is your Sprite for example.
And as an action, you would set the Sprite animation to the animation you want to play.