POO Encapsulation C #

I'm doing a modularity exercise in which I want to put in practice the encapsulation of data and methods.

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 

namespace Modularidad {

    class Program {

        static void Main(string[] args) {


            Modulo modulo = new Modulo(); 
            double resp = modulo.suma(3.5, 2.7); 
            Console.WriteLine("La suma es: " + resp); 
            Console.WriteLine(""); 

            Modulo1 modulo1 = new Modulo1(); 
            double pro = modulo1.multiplicacion(5.2, 8.3); 
            Console.WriteLine("La multiplicacion es: " + pro); 
            Console.WriteLine(""); 

            Modulo2 Modulo2 = new Modulo2(); 
            double resta = Modulo2.restar(4.3, 5.2); 
            Console.WriteLine("La resta es: " + resta); 
            Console.WriteLine(""); 

            Modulo3 Modulo3 = new Modulo3(); 
            double division = Modulo3.dividir(25, 5); 
            Console.WriteLine("La division es: " + division); 
            Console.WriteLine(""); 

            persona persona = new persona(); 
            string nombre = persona.nombre("Sasori"); 
            Console.WriteLine("El nombre del usuario es: " + nombre); 
            Console.ReadKey(); 
        }
    }


    class Modulo {

        public double suma(double n1, double n2) {
            double resultado = 0; 
            resultado = n1 + n2; 
            return resultado; 
        }
    }

    class Modulo1 {

        public double multiplicacion (double n1, double n2) {
            double producto = 0; 
            producto = n1 * n2; 
            return producto; 
        }
    }

    class Modulo2 {
        public double restar(double n1, double n2) {
            double resultado = 0; 
            resultado = n1 - n2; 
            return resultado; 
        }
    }

    class Modulo3 {
        public double dividir(double n1, double n2) {
            double division = 0; 
            division = n1 / n2; 
            return division; 
        }
     }

    class persona {
        public string nombre(string entrada) {
            string nombre; 
            nombre = entrada; 
            return entrada; 
        }
    }
}

My question is: How do I implement the encapsulation of the fields (objects) to my example?

I know I can use the three levels of access (public, private y protected) in the case of the "public" view if a method has this type of view, you can send it to the indicated method from any other class.

What I have not understood yet is

  

How to access an object with a "private" or "protected" view type?

since the object can not be accessed directly since (in the case of "private") the object can only interact within the class itself.

Investigating a bit uses properties for the fields in which "get" and "set" are used to assign and obtain values, but I would like to be able to apply all this to my example since I have not fully understood the functionality and Encapsulation application