There are two different approaches to customizing your macronutrient settings with Cronometer.
Dynamic Macronutrient Targets
Choose a preset ratio of protein:fat:carbs (Zone, Even, High Fat/Ketogenic, Paleo etc.) or set your own custom ratio.
This will dynamically calculate your macronutrient targets to achieve the ratio of macros based on your calories burned.
Use the default RDA values or edit each macronutrient target in the Nutritional Targets section to have the same grams-based target for each macronutrient each day.
To set your own custom values, first choose Fixed Targets under Macronutrient Targets.
Then, in the Nutritional Targets section (called Nutrient Targets in the mobile app), select the Carbohydrates tab, click Custom to override the default settings, then enter in your own custom value. Repeat this process for protein and fats.