That is a built-in reservoir for pre-heating alcohol (spiritus behälter, as you can see on that lid). It also has a pump that makes it easy to pump up the alcohol to the preheating cup. The pad on your second image is supposed to lay down horizontally, as seen in Wim's image here.
You shall have alcohol in it, yes. Alcohol which is used for preheating the lamp via the clever pump and little tubing up to the cup. I don't have one of these myself, but I'm sure someone who has one will help you with more details soon.
