As per your BMI , you are underweight.
Normal range is 18-23kg/meter square.
So you strictly do not need to reduce your BMI.
As for BMR, you can get it check by a machine called as Body composition Analyser. We have this facility at our clinic.
Next Steps
As to how much steps you need to do daily, generally if you are not used to any exercise till date, you can start with simple brisk walking for 30-35 minutes daily to stay fit and healthy.
Health Tips
Contact a qualified Dietician who can check your body fats, muscles, bones weight, your BMR and guide you exactly what should be your calorie intake and how much calories you need to burn daily.
Just to add, we also do online diet Consultation