The website really does not include a proper specification.
The website offers a golden nugget though:
voltage: 2 x 12V
This appears to mean that you have two independent 12 volt secondaries which you could connect either in series or parallel.
Also, it is implied that the transformer *only* works from 230 volts...in other words, it is not an universal 230/115 volt device.
This simplifies things *a lot*.
As suggested earlier, find the terminals with the thin wire; those will be your 230 volt input. You can safely connect them to the mains.
Then with a multimeter, identify the pair of secondary 12 volt windings. NOTE: with no load the output voltage will be around 16 volts, that is perfectly normal.
Now, take one terminal from one of the secondary 12 volt windings and connect it to any other terminal of the other 12 volt winding.
Power up the transformer and take a reading with the multimeter across the free terminals. If the voltage is between 24 to 32 volts, congratulations, you have it made.
On the other hand, if the voltage is zero or very close to zero, unpower the transformer, and swap one terminal of only one of the windings.
Power again and measure...your voltage should be there.
For the next time you purchase a component, a lesson learned:
The lesson I've learned over the years not to purchase anything from the web which does not include a proper datasheet or drawing....unless it is so cheap you can afford to damage it during the course of your experiments.