The reason it's not on the OW site is that lounge access based on class of service flown is not a oneWorld benefit. It's a benefit each airline offers to its own premium class passengers. There is no coordination of policies in that regard within oneWorld, though they are all pretty similar because the entire airline industry is pretty similar in that regard.

Lounge access based on elite FF status with any OW partner is on the site, though. You probably found that part. For anyone else: click Benefits at the upper right. There's an overview of lounge access at the bottom of the page. For specifics, click on the airline where you have elite status (not the one you're flying on). There will be a pull-down menu for its elite levels. Choose yours, click "Show me" below the menu, and it's there.