That's like posting a question "How do I drive a car?"
Then provide some details for what you are trying to do, the steps you've taken in LabVIEW, and where you are stuck.
Simple: Use a US-piezo disc, connect it to the line in of your soundcard.
If an object is crashing the piezo, you get a signal and you know the distance is zero 😄
Serious: look for a sensor that matches the connection capabilities you have.... and the budged you have 😉