I have the following code to show how long a user has left before their session will expire, I am using WordPress. How can I do this? Thanks

    <script>
    var obj_Span;
    var n_Seconds = 0;
    var n_Minutes = 0;
    var n_Hours = 0;

    function F_ConvertNumberToString ( n_Num )
    {
        var str_Num = String(n_Num);
        if ( str_Num.length < 2 ) str_Num = "0" + str_Num;
        return str_Num;
    }

    function F_CountDown ()
    {

        if ( n_Hours == 0 && n_Minutes == 0 && n_Seconds == 0 )
        {
            obj_Span.innerHTML = "(Sorry, your session has expired.)";
        }

        else
        {
            if ( n_Seconds >= 0 ) n_Seconds --;

            if ( n_Seconds < 0 )
            {
                n_Minutes --;
                n_Seconds = 59;
            }           

            if ( n_Minutes >= 0 )
            {               
                window.setTimeout ( "F_CountDown()", 1000 );
            }

            if ( n_Minutes < 0 )
            {
                n_Hours --;
                n_Minutes = 59;
                window.setTimeout ( "F_CountDown()", 1000 );
            }           

            F_UpdateDisplay ();     
        }       
    }

    function F_UpdateDisplay ( )
    {       
        if ( document.getElementById )
        {
            if (n_Hours > 0 ) obj_Span.innerHTML = "(Remaining " + F_ConvertNumberToString(n_Hours) + ":" + F_ConvertNumberToString(n_Minutes) + ":" + F_ConvertNumberToString(n_Seconds) + ")";
            else obj_Span.innerHTML = "(Remaining " + F_ConvertNumberToString(n_Minutes) + ":" + F_ConvertNumberToString(n_Seconds) + ")";
        }
    }

    function F_StartCountDown ( n_Session )
    {
        obj_Span = document.getElementById ( "CountDown" ); 
        n_Minutes = n_Session;
        n_Hours = Math.floor(n_Minutes/60);
        n_Minutes = n_Minutes - (60*n_Hours);
        F_CountDown (); 
    }
</script>

<script>
    F_StartCountDown ( " code here... " );
</script>

<span id="CountDown"></span>