Because of the limited space in Facebook’s impressum text box, it’s now become common practice to add an external link to the impressum page of your business website. If you decide to go down this route, you should link directly to your impressum, and not just to the website’s homepage. Additionally, it’s important to indicate clearly that the link leads to the impressum; links should therefore always be named and labelled clearly to ensure visibility and accessibility. You could also include a relevant anchor text, appropriate URL, and/or an explanatory note.
The impressum itself should also include a note that the same information applies to all your social media platforms, and provide links to these sites (including Facebook, Twitter, Google+, etc.).