The throttle is loose by default for more safety during transport. Have a look at this video: https://drive.google.com/open?id=1qVW0HqoNos3y-zjZ-JjaTGVDia-qlyE3
If you do not have the screw, let us know. We can send you a new one. Alternatively, you can pick one up at any hardware store. It is a 5mm screw like this.