@Karthik-Bharadwaj You'll need to insert this into the unused XT30 connector: https://www.modalai.com/products/mcbl-00109?_pos=1&_sid=cc83b4694&_ss=r
3A is more then enough to power the drone on the bench, just make sure never to spin motors on wall power! (You can damage the drone and will not be able to RMA it)
In order to disable arming you'd have to look through the PX4 parameters