Timer Start on Gui from function

In my Unity Editor i have within my canvas a time remaining input field(TimeRemaining). What i'm trying to do is when the game starts have this countdown automatically, and display the time remaining in the textfield. In my countDown class i have the following code:

 public class countDown : MonoBehaviour {
     float timeRemaining = 5;
 
     public void RunClock()
     {
         timeRemaining -= Time.deltaTime;
         if (timeRemaining > 0)
         {
            // This is where i guess I would need to connect the timeRemaining and the textfield component. 
         }
         else
         {
             // Do something to end the game
         }
     }
 }

Connected to the TimeRemaining Inputfield, i have an object connected as a component. And within that object it holds the script for the above.

The game gets started from another script where i call the Start() function.