Lerp takes 3 perameters, a a, b and c.
the a is allways the start of what your lerping, It tends to only work if you call something like: sprite.opacity. ect then b is what you want it to lerp to, so if i want the sprite to animate from a opacity of 100 to 0 then i set b to 0. And c is the time it takes to do it. Usually 0.8 is a nice number buy you can play around with it. and then you times the number by dt this just makes things happen in real time.
So for a opacity of 100 to 0:
Sprite.setOpacity{lerp(Sprite.Opacity, 0, 0.8*dt)}
To animate its x position to the center of the stage:
Sprite.setX{lerp(Sprite.x, WindowWidth/2, 0.8*dt)}
To animate its y to center of stage:
Sprite.setY{lerp(Sprite.y, WindowHeight/2, 0.8*dt)}
Hope that was some help.