Reference management software (also called bibliographic management or citation management) can save you a great deal of time and effort when you are writing a paper, dissertation or thesis.
It enables you to store the references you collect while searching the literature, and will automatically format the citations in a word processor document, and produce a list of references at the end of that document formatted in the style of your choice (e.g. Harvard, Vancouver).
There are lots of reference management software packages to choose from: some require a subscription and some are free. QUB subscribes to and offers support on Endnote.
The link below takes you to the Referencing subject guide.
Below is a link to a useful online guide explaining the importance of referencing and outlining some of the key styles.
Academic research, writing and referencing by 
The Complete Guide to Referencing and Avoiding Plagiarism by To reference NICE guidelines you will need:-
Format:-
Corporate author's name (year of publication or update if there has been an update) Title of guidance: type of guidance and (its letternumber combination). Available from: www.address.com [Accessed: day month year].
Example:-
National Institute for Health and Care Excellence (2018) Post-traumatic Stress Disorder (NICE guideline 116). Available at: https://www.nice.org.uk/guidance/ng116 [Accessed: 16 August 2019].
In text citation:-
(National Institute for Health and Care Excellence, 2018)
NB after the first citation you can abbreviate National Institute for Health and Care Excellence to NICE