After importing the HC-SR04 Ultrasonic Sensor Library there will be a notice (near the bottom left of the IDE window within the green bar) confirming installation:
“Library added to your libraries. Check ‘include library’ menu”.
You can confirm the library installed via “Sketch” > “Include Library” : see the “HC-SRO4” entry in the menu within the screenshot below.
The HC-SR04 Ultrasonic Sensor Library can be included within a Sketch like any other Arduino Library.
Continue Reading How to Install Additional Arduino Libraries