1) Type the term you are looking for into the search box.
For German words, umlauts (Ä, ä, Ö, ö, Ü, ü) and the "scharfes S" (ß) should be entered like that, otherwise the search results may be incomplete! (For example: a search for "Königsberg" returns numerous hits, whereas a search for "Koenigsberg" returns only very few.)
2) To the right of the search box you can select whether you want to search the entire site (the results may then include English and German pages) or whether you want only English or only German results.
3) Then click on "Search"!