Create the fields in class level then instantiate inside methods or create and instantiated inside methods

I'm a newbie in software development. Just wondering which code is better and why should I continue which pattern should I follow.

First Snippet:

Class TestClass
{
    private Object1 field = null;
    private Object2 field2 = null;

    public void TestMethod1() 
    {
          field = new Object1();
          field2 = new Object2();     
    }

    public void TestMethod2() 
    {
          field = new Object1();
          field2 = new Object2();     
    }
}

As you can see, I created fields in Class level and instantiate them inside the method.

Second Snippet:

Class TestClass
{

    public void TestMethod1() 
    {
          Object1 field = new Object1();
          Object2 field2 = new Object2(); 
    }

    public void TestMethod2() 
    {
          Object1 field = new Object1();
          Object2 field2 = new Object2(); 
    }
}

Here I created and instantiated the fields.

These fields are being used over and over in many methods in a class.