Hopper Fresh Presses are only compatible with Pinter 2. Unscrew the Hopping Cap from the back of the Pinter. Take the Hopper, remove the metal cap but do not remove the foil seal. Firmly hold the Pinter down and screw the Hopper all the way in until it's flush. Remove the Hopper and replace the Hopping Cap until flush with the back of the Pinter.
Refer to the instructions for further details - you can find them here.