Assuming you would like to do a search on google.de (the German version of google), simply go to google.de and enter your search terms as usual.
If you're using google.com (the US version of google), you can specify that you want to see results from google.de by clicking on the "Settings" icon (the one that looks like a cog) in the upper right-hand corner of the page, and then selecting "Search Settings" from the drop-down menu. On the "Search Settings" page, scroll down to the "Region" section and select "Germany" from the drop-down menu. Then click "Save" at the bottom of the page. Your results will now be pulled from google.de.