Step 6: Thread wires through tube
Insert the wires soldered to the sensor through the enlarged end of the tube and pull them out through the other end. The sensor should, when you pull on the wires, be drawn into the flared end of the tube.
Identify the wires at the other end and label them now, because, once the sensor is fixed inside, it is virtually impossible to tell them apart. It would be a good idea to measure and make sure no short circuits exist.
Using the diode check range of the multimeter, the three leads will either show 'open' or as a diode. A reading of zero ohms should be cause for consternation.