There's lots of ways to do this. One way I like to do this is with Tween
Here's an example if you're throwing it to the left
tween "x" to self.x - 200 over 2 secs (linear)
tween "y" to self.y - 100 over 1 sec (out sinusoidal)
wait 1 sec
tween "y" to self.y + 100 over 1 sec (in sinusoidal)
the out sinusoidal followed by the in sinusoidal will give it a nice arc that looks like gravity
you can tweak these values until it feels right