This is the main reason you took this tiny little device home I guess. I hate to look around the house just to find my car key in the early morning. It happened too many times for me so it might be the same case for you.
How to find iHere/Car Key Finder
Now you may just open your iHere app, click the left "FIND" tag and click "Find" button. The device would beep and you could locate it easily.
How to find your Phone
You may press the iHere/Car Key Finder and your phone would ring as a call. Press again and the ringing would stop.
*UI might be different for the app of newest version