What is the basic principal of eating as a diabetic?

I have recently been diagnosed as a “borderline diabetic”. I am almost 41 years old. I have illiminated sugar and white flour to the best of my ability from my diet and eat three meals a day with a snack in the evening.
So far, I have lost 15 pounds in 30 days; my current weight is 235.0 lbs and I am 5’10”. My question is, what is the basic principal of eating as a diabetic? Is there an amount of protein/carbs/fat that one should eat to maintain a constant glucose level in the blood? Or a specific timing? Thank you so much for your help.