How to add utf8_encode to my php code

<?php  
        $mysqli = new mysqli("localhost", "root", "", "lista");     
        if ($mysqli->connect_errno) {
            echo  "Fallo al conectar a MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;
            exit();
        }
        $consulta= "SELECT * FROM lista";
        if ($resultado = $mysqli->query($consulta)) 
        {
            while ($fila = $resultado->fetch_row()) 
            {               
                echo "<tr>";
                echo "<td>  $fila[0]</td><td>$fila[1]</td><td>$fila[2]</td><td>$fila[3]</td><td>$fila[4]</td><td>$fila[5]</td>";    
                echo"<td>";                     
                echo"<a data-toggle='modal' data-target='#editUsu' data-id='" .$fila[0] ."' data-agencia='" .$fila[1] ."' data-departamento='" .$fila[2] ."' data-area='" .$fila[3] ."' data-nombre='" .$fila[4] ."'data-extencion='" .$fila[5] ."'class='btn btn-warning'><span class='glyphicon glyphicon-pencil'></span>Editar</a> ";            
                echo "<a class='btn btn-danger' href='elimina.php?id=" .$fila[0] ."'><span class='glyphicon glyphicon-remove'></span>Eliminar</a>";     
                echo "</td>";
                echo "</tr>";
            }
            $resultado->close();
        }
        $mysqli->close();   

? >