Hilton's latest promotion is simple in application. You will earn double the points for all paid stays between 9th September 2019 – 5th January 2020. In order to qualify you must register via this link first.
The points gained from the ‘Power Up' promotion is in addition to any status bonuses you might earn, and you will earn bonus points for ALL stays. Also check our Beginners' Guide to Hilton Honors to understand what elite bonuses apply.
Note that if you have a Hilton-branded credit card, if you pay using that you will earn TRIPLE points instead. (Unluckily for me I cancelled mine some time ago!)
All new and existing bookings, so long as they fall within the dates mentioned above, will qualify for the double/triple points. You just need to make sure you are registered first.
An abbreviated terms and conditions are below, but you should also check here for the full wording.