The link for the beta app is directly underneath your code for the FF14 item.
You can go back to the Squeenix MEMBERS page, go to the FF13 section, and click Bonus Codes, it should still be there.
I have very few options on the Members site. Just Home which is a banner showing some S-E games, and Account which shows I have one game registered, which I can't click on. I can only edit my personal details or add another game.
Is the promotional code only for those in the US maybe?