There are no written guidelines in APA on citing social media. However, the APA style blog (http://blog.apastyle.org/apastyle/social-media/) suggests:
Facebook:
Title of Facebook Page. (year, month day). Title of post. URL of post [Facebook update]. URL of Facebook page
Twitter:
Title of Twitter Page. (year, month day). Title of post. URL of post [Twitter post]. URL of Twitter page.