Welcome to Apug, Baudoin !
Well, I wonder why you not just tried it... in any case you have to put the timer in between the enlarger and the mains.
You may check the max load the timer takes, some timers state such, but in most cases they should be sufficient for most enlargers. Likely yours takes 1000W.
Set the time in seconds and push the button to start the timer. Most timers have a overrun switch, that makes the light burn without the timer to run, which is most useful for focusing.
Basically there are two types of mechanical timers:
Spring loaded ones and ones driven by an electric motor. The former ones typically have a moving dial. The latter ones typically a static dial, so that one is able to repeat a time set once.
Yours seems to be of the latter type (I got a very similar model from Hauck). For focusing your push button got an arrest position at pulling up the button.
The timer at the second photo in addition got a factor-switch (likely factor 10 that enables to use it within a 600sec range)
(At mine there even is a slight error at the manual...)