The World Health Organization (WHO, 2018) states that...
...(World Health Organization (WHO), 2018).
WHO (2018) states that...
Note: A good tip if you are going to use the same citation a few times in your assignment is to use acronyms. You must explain the acronym in full the first time you use it, followed by the acronym so it is clear to your lecturer what is stands for.
Last name, Initial(s) or Group Author. (Year, Month Day). Title. Website name. URL
Gallagher, J. (2020, August 4). Testing and tracing 'key to schools returning', scientists say. BBC News. https://www.bbc.co.uk/news/health-53638083
World Health Organization. (2018, May 24). The top 10 causes of death. https://www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death
NB: When the author and website name are the same omit the website name to avoid repetition.