If you really want to make it big, don't confine yourself to "learn WordPress website". Learn PHP, MySQL, Javascript and HTML/CSS. WordPress is just a cms. If you're familiar with the aforementioned technologies, WordPress will be a piece of cake for you.
As for "where", you can start by looking in the download and giveaway section in bhw. What you are looking for are good courses, that are shared for free.
Also remember: YouTube, Stackoverflow and google are your friends when it comes to learning programming (or anything for that matter). Whenever you get stuck, "Search"!