How do I get a value from a datatable

autkiller97

I have tried and googled just to find no solution.
I want to get a value a selected row of my datatable (the ID) but i dont how to do so.
The value shoud be given to a textbox

Here is my Code:
var oTable = $('#dataTable').dataTable();

    $.ajax({
        url: 'process.php?method=fetchdata',
        dataType: 'json',
        success: function(s){
        console.log(s);
                oTable.fnClearTable();
                    for(var i = 0; i < s.length; i++) {
                     oTable.fnAddData([
                                s[i][0],
                                s[i][1],
                                s[i][2],
                                s[i][3],
                                s[i][4], 
                                       ]);                                      
                                    } 

        },
        error: function(e){
           console.log(e.responseText); 
        }
        });

    $('#dataTable tbody').on( 'click', 'tr', function () {
    if ( $(this).hasClass('selected') ) {
        $(this).removeClass('selected');

    }
    else {
        oTable.$('tr.selected').removeClass('selected');
        $(this).addClass('selected');

    }
} );

Hopefully someone can help me!