How much total calories should I be eating a day (male, 5'9, 19 yrs, 170 pounds) and how can I keep track with how many calories I eat?

You could install a calorie tracker mobile app (most of these apps also track your macro-nutrients), or you could go with the good old fashioned food log.

According to www.calculator.net/calorie-calculator.html , you need about 2,450 calories to maintain your weight if you are lightly active.

They have calorie counter books and probably a app for it. Sounds like your a little under weight but its up to u