Point System Help?

Hey Unity Users, i need help with a little script just to test adding points but it wont let me add 2 intergers(int), i want a little thing where i press “H” and it increases the ZPoints by 10 and if i Press “K” It increases the ZPoints by 60

using UnityEngine;
using System.Collections;

public class ZPoints : MonoBehaviour
{

	void Start ()
    {
        //efefe
	}

    public void Intergers()
    {
        int ZPoint;
        int HMark;
        int Kill;

        ZPoint = 500;
        HMark = 10;
        Kill = 60;

    }

    public void ZCount()
    {
        if (Input.GetKey("k") || Input.GetKey("K"))
        {
            ZPoint + Kill;
        }

        if (Input.GetKey("H") || Input.GetKey("h"))
        {
            ZPoint + HMark;
        }
    }
}

Just put ZPoint += Kill;

and Zpoint+=Hmark;

ZPoint += Kill is the same as ZPoint = Zpoint + Kill;

Which is what you want to do.