linking your social accounts means that you have to link your social account once with your SAP Cloud Identity account and from then on you could also use your social account for log in. In order to do so you need to trigger this one-time linking from the login page. So call for instance people.sap.com which will show the login page, then choose one of the social icons e.g. Twitter shown below the Log On button. You will get prompted to provide your Twitter credentials, then you need to provide your normal SAP Cloud ID credentials (the ones your are using to log into SCN) and the linking is done. Next time you want to log in you can directly click on the Twitter icon and use the Twitter credentials.