For this task, you'll need the Hot End Assembly, the Probe PCB, and the Locking PTC Adapter.

The Locking PTC Adapter has a PTFE tube in it. Remove the tube from the adapter before you begin.

Insert the PTFE tube into the top of the heat sink until only 4 or 5mm are exposed at the top.

The PTFE tube has a taper on one side of it. This side should face the top of the heatsink on the side with the circuit board.

Center the Probe Board on top of the heat sink with the bottom JST connector aligned with the thermistor and install the threaded Locking PTC Adapter. When you install the adapter, thread it in slowly - stop when you feel the adapter begin to compress the PTFE tubing.

Fix the PCB and Hot End together by tightening the locking nut as indicated by the red arrow. Tighten with the blue plastic HE280 PTC tool (not shown).