Instanciar function in laravel

What would be the best way to instantiate an external function within a controller in laravel?

I have the following code:

<?php

namespace App\RandomCode;

class RandomCode
{
    function Generate()
    {
        $caracteres = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890"; 
        $numerodeletras=8;
        $cadena = "";
        for($i=0;$i<$numerodeletras;$i++)
        {
            $cadena .= substr($caracteres,rand(0,strlen($caracteres)),1);
        }
        return $cadena;
    }
}

in the App\Class directory, which I need to call it within a controller.