You need three points and a sprite. The first and last point are the endpoints and the middle point controls the curve. In the most simple example you would setup the events like this:
global number t=0
--- set t to min(1, t+1*dt)
--- sprite: set x to qarp(p1.x,p2.x,p3.x,t)
--- sprite: set y to qarp(p1.y,p2.y,p3.y,t)
the "1" in t+1*dt is the number of seconds it takes to move.
The min() expression is used to make it stop at the end. otherwise it would keep going.