Attack move help

Attack Move, is when you press "A"(which is the default key) and left click on the screen. Your champ will move to that location then attack its target. However, if you just click on a space in the ground. Your champ will attack the nearest target closest to your Attack Move point

Basically, it moves you somewhere but if something attack-able is nearby at any point during your movement you'll attack instead. It's basically attack and move in one command but the attack overrides the move. Great for kiting on ADC's and also using for checking bushes and stops them from doing that silly move-out-of-the-bush-before-you-click-me juke that people do.

But I don't get how to use it. Do you hold down the button? That doesn't seem to work.