For testing your code for the Mega 4808 with Arduino you need a board where every pin is accessible. Here is the Mega 4808 minimal board.
Only connect a 1.8V – 5V power supply to VCC and Ground and the board works. It can be programmed over the UPDI Pin.
Here you can read how to start with the Mega 4808 and Arduino.
Other posts about Mega 4808: