These are online sources and so should be referenced as such. Do consider if this is an appropriate source to be using in an academic context.
Format: in text citation
The University of Northampton Life series documents stories from UoN students (Surname/Organisation name, Year).
Surname, Initials. (Year) Title of page. Facebook [online]. Day/month post written. Available from: URL for specific Facebook post [Accessed date].
Example: in text citation
The University of Northampton Life series documents stories from UoN students (University of Northampton, 2019).
University of Northampton (2019) University of Northampton. Facebook [online]. 4 February. Available from: https://en-gb.facebook.com/UniversityofNorthampton/ [Accessed 27 February 2019].