Can I tag people or pages in my posts?
For Twitter, you can insert a username into your post by entering it like this: @username
You'll need to know the Twitter username you wish to tag first though as, when you type the "@" symbol into the post text box, matching usernames do not appear for you to select.
To tag a Facebook page in your posts (currently, you can't tag people), the tag has to be entered like this: @pageid
You can find the ID of any Facebook Page by following these steps.