Set your calorie and macro goals
Get a suggested plan, then adjust it.
Go to Profile → Goals.
Nutri suggests calories, protein, carbs and fat from your sex, birth year, height, weight, activity level and, if you set one, a goal weight and pace. You can type these or fill them from Apple Health.

Goals are guidance. Nothing turns red and there is no penalty for going over.
Units and region
Switch between metric and imperial, and choose your data region (US or Canada), in Profile.