How to reference a GameObject in Unity properly?

I have created the GameObject Character in Unity with sprites however i cant figure out how to reference it in the script so the buttons can cause the Character to jump and move. I already have it working so keys on a keyboard will make the character move but im trying to transfer that code so it can work with the buttons i created instead. Help please, im very new to unity so any advice would be much appreciated!

public class GUItest : MonoBehaviour { void OnGUI() { if(GUI.RepeatButton (new Rect (0,Screen.height - 30,40,25), "Left")) { GameObject.Character.GetComponent().FixedUpdate(); Debug.Log("Clicked left"); } }