HR Zone Running

Looking into utilizing HR zone running in my training and would love some tips! I have a Garmin Forerunner so it creates my zones automatically for me but not sure how accurate that is vs making them myself! My average HR for my long runs is 170-180 so I know I need to get it down BUT I’m also a newer/slower runner so I’d love some advice for training to help with this! I try to do a speed workout, 20-30 minute nice slow easy run and a long run (just got up to 6 miles for the first time today as I’m training for my first half marathon in March)! Also read a lot about zone 2 training but not sure how to calculate it as I’ve seen so many different things! My max HR is 197 usually and I’m about to be 25 in like a week!