This was shown after the Christmas special. It’s available to watch on the BBC Doctor Who site, which may or may not work for people outside the UK.
And here it is, subject to the usual YouTube “there until somebody complains” rule:
Looks like fun. Remember that it’s a split series this year, with seven episodes starting in the Spring, which will end with a humungous cliffhanger, then returning in the Autumn for six more. River Song is in it from the beginning, as far as I can currently tell, and we’re due to find out a lot more about her, and about The Silence, whatever that (or, as Mr Moffat suggested somewhere, they) might be.