The link for the ultrasonic sensor appears to be down. Ostensibly, you could just go here instead. Also, this one appears to be virtually identical.
And, by all means, feel free to check them out. There might be some interesting reading.
However, that isn't where I'd suggest getting the ultrasonic software from. The Arduino IDE has what looks to be the best option now.
Disclaimer: If you're in the second lab of the week, you might be able to skip this step.
In the Arduino IDE, click Tools, then Manage libraries.... In the window that pops up, type ultrasonic into the search. If you scroll down, there are a few options, but the one by Gamgine appears to work quite well. (It'll stand out, because there's also a version drop-down for it)
Anyhoo, install that (if it isn't already), and under the File menu, for Examples, if you scroll down enough (you'll probably have to hover the cursor at the bottom), you should see a very basic rangefinding example.
You don't have to do things this way. It just appears to be the simplest.