Simply go to http://www.linkedin.com/opensocialInstallation/preview?_ch_panel_id=1&_applicationId=2600 and click on Add Application and follow the prompt to log in to your SCN (SAP Community Network) account.
Thanks to the comments on this blog I must also mention that you need to have enabled LinkedIn on your business card. To do that click My Profile -> Update Profile.
Click Update Business Card and click “Activate LinkedIn Connection as shown below.
Once integrated with your LinkedIn account your profile looks something like this: