Tips for a beginner at the gym?

You should begin your first workout with a warm-up consisting of 10-20 minutes of walking or jogging or other aerobic exercises.
Have a Plan and Track Progress
Don’t be Afraid to Ask for Help. Ensure you perform each exercise safely and effectively.
Choose the Right Weight: Loosen up with a few very light exercises first, then choose a weight that is heavier and that starts to feel somewhat heavier as your muscles tire; don't do too much too soon.
Choose simple compound exercises like the squat, bench press, deadlift, pull-up, lunge, and bent-row. Avoid complex exercises too soon.

Lastly, DON’T COMPARE YOUR DAY ONE WITH SOMEONE ELSE’S DAY 100.
Be patient, consistent and you will see the results in due time.