Before deploying multi language support you need to download the wanted language pack for SharePoint from Microsoft web site. Check out this older post – Adding language packs to SharePoint 2010 which describes how to get and deploy the German language pack.
Then if you are not already using a Publishing site template on your site collection, you have to enable the Publishing Infrastructure. This is done in two steps:
- at the site collection features level: click on Site Actions -> Site Settings -> Site collection features (Under Site Collection Administration) and activate SharePoint Server Publishing Infrastructure
- at the site features level: click on Site Actions -> Site Settings -> Manage site features (Under Site Actions) and activate SharePoint Server Publishing