lay the card down so the fans are facing the table. unscrew all the screws on the back of the card, if the card has a backplate it should be loose now. Make sure there are no other screws under the backplate, if there are take those out. turn the card over and gently twist the cooler on the card, that will break the bond of the thermal past. If it doesn't move freely you might have missed a screw, if it does move freely then gently pull them apart. There will be past on the cpu and thermal tape on the memory, when you get the waterblock ther will be instructions on where to apply new tape and paste.