Claxon:
I changed the file type from a .cpp to .ino to get the arduino software to open the file.
That will allow you to open the file but it's not going to compile because that's not a sketch, it's a library. Libraries contain code that you can access from your sketch by #include-ing the library header file but they are not complete programs in themselves.
In order to use the Adafruit Fingerprint Sensor Library you first need to install it:
- Sketch > Include Library > Manage Libraries
- Wait for the download to finish.
- In the "Filter your search..." box, type "Adafruit Fingerprint Sensor Library"
- Click on the Adafruit Fingerprint Sensor Library entry.
- Click "Install".
- Wait for the installation to finish.
- Click "Close".
After doing this you will find example sketches under File > Examples > Adafruit Fingerprint Sensor Library that demonstrate how you can use the library in your project.