If you're wanting to do it via the Main method, then the most logical means is to receive the deposit/withdraw amounts as input from the user, which would be the case in a bank application. Then just simply output their input. As well, you could also create getters in your class for it. 
Give me a moment and I'll type up example that depicts both ways. 
EXAMPLE (DISPLAY VIA MAIN):
https://code.sololearn.com/c9hr3bwfWUFO/#cs
namespace SoloLearn
{
    class BankAccount { 
        private double balance=0; 
        public void Deposit(double n) { 
            balance += n; 
        } 
        public void Withdraw(double n) {
            balance -= n;
        }
        public double GetBalance() {
            return balance;
        }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            double depositAmount = 0;
            double withdrawlAmount = 0;
            BankAccount b = new BankAccount();
            
            // Get user input for Deposit amount and display
            depositAmount = Convert.ToDouble(Console.ReadLine());
            b.Deposit(depositAmount);
            Console.WriteLine("Deposit Amount: " + depositAmount);
            
            // Get user input for Withdrawl amount and display
            withdrawlAmount = Convert.ToDouble(Console.ReadLine());
            b.Withdraw(withdrawlAmount);
            Console.WriteLine("Withdrawl Amount: " + withdrawlAmount);
            
            Console.WriteLine("New Balance: " + b.GetBalance());
        }
    }
}