you will need a pump, radiator, fittings, tubing and reservoir to liquid cool this card. it will cost you 200-300USD depending on the parts selection.
it's basically takes to build a custom loop to liquid cool this card.
Another option would be using an expandable AIO like Swiftech H240 X2. this way you also add the CPU to liquid cooling.
As a side note, this probably not the most cost/performance effective way. if you want to liquid cool the GPU, just get much cheaper 1080Ti that is based on reference design and get an EK fluid gaming kit. depending on your case and room temperature, you might want to add another radiator.
Instructions on how to do that can be found on youtube - check out JayzTwoCents channel. he have plenty of...