Did you read sketch comments?
* 1. Optional, but recommended.
* Connect additional USB-serial adapter to see the prints.
*
* 2. Edit auth token and upload this sketch.
*
* 3. Run the script (script located in "scripts" folder of library root,
* e.g. 'blynk-library/scripts') for redirecting traffic to server:
*
* for Windows: blynk-ser.bat
* for Linux and OSX: ./blynk-ser.sh (may need to run with sudo)
*
* You can specify port, baud rate, and server endpoint like this:
* ./blynk-ser.sh -c <serial port> -b <baud rate> -s <server address> -p <server port>
*
* For instance :
* ./blynk-ser.sh -c /dev/ttyACM0 -b 9600 -s cloud.blynk.cc -p 8442
*
* Run blynk-ser.sh -h for more information
*
* Be sure to select the right serial port (there may be multiple).
*
* Attention!
* Arduino IDE may complain with "programmer is not responding".
* You need to terminate script before uploading new sketch.
*
* 4. Start blynking! :)