Can you use the same domain to point to two different websites?

I have built a ‘microsite’ for my client’s 2022/23 annual report. They have an existing ‘main’ Squarespace website built by someone else (https://www.janga.la/) and have requested that this new ‘microsite’ sits under the same domain as their main website. E.g:

www.janga.la = main website (SS website 1)

www.janga.la/annual-report = microsite (SS website 2)

Does anyone know how to achieve this? 

They provided a live example from another charity ‘Education Cannot Wait’. Note how the domain remains the same:
 

https://www.educationcannotwait.org (Main website)

https://www.educationcannotwait.org/annual-report-2021/ (Microsite)

Thank you in advance, this is not my area of expertise! Matt