I already used it for another warframe giveaway, and at that time i arrived there directly from the app.
Also, i just now noticed that the desktop omen hub actually links to it, you have to click on fanatical in the left tab, and then the request bundle button for the pack on the rotating banner in the page (i just didn't see it before).
Last time i'm sure there was a section dedicated to giveaways on the app