It is for new subscribers to their emails only. You have to go to the root of their website with all your ad blockers off & a pop-up for the competition will appear - I had to disable both Firefox's inbuilt protection and Privacy Badger for it to appear.
No idea what happens if you're already subscribed though, it'd probs let you enter but be an invalid entry.
This is just a link to the terms and conditions, where's the actual competition?