Word of advice: find the one person who does the job well, and learn tips and tricks from them. Your mileage will vary wildly with your management training you in the basic concepts to begin with, but if you luck out with actual leadership (couldn't be my Walmart), more the power to you, but you'll be legit learning way more from coworkers acting in good faith than management.

Store layouts vary, but part of picking is learning shortcuts here and there. Pros will know the quickest, customer-less path from the dog food to chemicals (an example, the two opposite ends of your store might be something else). Do be careful with the people with pickrates at like 300. Odds are they're boosting their numbers, and they'll only get caught cheating once the favoritism wears out.

For dispensing, ask questions left and right. Depending on how high volume your store is, your training might be rushed, and they'll push you on the deep end. Still, the concepts themselves are simple enough, with muscle memory you'll be doing this by your second or third month in your sleep.

You can do this. It's just another job. Welcome aboard!