Sure, in the squat you'll walk the weight out, get in your stance, nod to the head ref to communicate you're ready to squat and you will be given the verbal command squat. After receiving the verbal cue all you can do is squat down, break parralel and stand back up, move your feet and you'll be red lighted. After standing back up wait for the verbal cue rack, then you can rack the weight.
In the bench, after unracking the weight in some feds you have to wait for a start command in some you don't. Bring the bar down and touch your chest and wait for the press command to press the bar back up. Wait for the rack command before returning the bar to the bench rack.
Deadlift is pretty simple, grab the bar in your stance, stand up, receive down command, set the bar down, don't let go of the bar, and you'll be good as long as your form was acceptable.
Powerlifting federations vary somewhat with their rules, different feds allow different things regarding technique, walk outs versus monolifts, benching on the balls or flat footed. Check the rules of the fed you will compete in and make sure you are fimiliar with how to comply with them.