The Harvard referencing style for the website article on Growth mindset vs fixed mindset would be:
Author Last name, First initial. (Year). Title of article. [online] Available at: URL [Accessed Day Month Year].
For example, the reference for the website article mentioned in the prompt could be:
Smith, J. (2014). Growth mindset vs fixed mindset. [online] Available at: https://www.examplewebsite.com/growth-mindset-vs-fixed-mindset [Accessed 15 February 2022].