How to Confirm a 3rd Party Arduino Library was Installed

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.