A relay is just a switch turned on and off by an electrical signal, thus allowing a low voltage signal (5V) from the Arduino to turn a high voltage (230V) line on and off
From the wiring diagram it looks like the switch labelled U moves the carousel forward when closed. Wire the normally open relay contacts in parallel with it and the Arduino can move the carousel forward by applying 5V to the relay coil
The programming is easy. Use the Arduino Blink sketch to control how often the relay is operated and you are in business.