Muller TC 24.21 Timer Wiring Help
The datasheet clearly says "Supply Voltage 230 V, 50/60 Hz", so I would connect a 230 V "Hot' wire to the "L" terminal, and the neutral wire to the "N" terminal.  The timer would connect terminal 1 or 3 to L, depending on the state of the timer, so you would connect your 230 volt load between either 1 or 3 and N.

It appears that you can connect a switch between L and Ext to start/stop the timer.

With luck, there should be a more detailed user manual included with the timer.