The PCB must be mounted floated, otherwise key presses don't work reliable. Connect pins 3 and 4 on connector P1 for 16-pin button mode. Smaller keypads with less pins may work, but are not tested.

Copy the "TTP229" library folder to your /libraries/ folder. Restart the IDE (close and open again). Then in Arduino IDE: File -> Examples -> TTP229 -> KeyToSerial. File -> Examples -> TTP229 -> ...