Check out example codes for "what is the namespace for textmesh pro". It will help you in understanding the concepts better.

Code Example 1

using TMPro; //This namespace allows you to use TMP related actions

public GameObject GameObject //Second word is variable type
//Make sure you make a ref. in inspector   //You can name the 3rd word whatever
  
GameObject.GetComponent<TextMeshPro>().text = "Whatever";
  				//above is the special TMPro name space

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