Have not messed with them in almost 15 years. They were pretty easy to use. The UT modules usually have a voltage and ground lines and a single send/receive line. You would send a quick send blip on the send/receive line and then would check for a return voltage blip on the line.
In my case it was a microcontroller that was controlling the module and calculating distance based on number of CPU clocks between sending and receiving blip.
Would guess they have even made them easier to use since then. Think we used to order them from DigiKey.