How can i install version 10.12.0 on my late 2008 macbook pro?
The latest version of Mac OS X for a Late 2008 MacBook Pro is OS X 10.11.6, and therefore if the requirements for the version of MS Word your university is using is macOS 10.12.0, you'll not be able to install it.

From the Microsoft website:


  Operating system Office 2019 for Mac is supported on the three most recent versions of macOS. When a new version of macOS is released, the Office 2019 for Mac Operating System requirement becomes the then-current three most recent versions: the new version of macOS and the previous versions.
  
  Product functionality and feature availability may vary on older systems. For the best experience, use the latest version of any operating system specified above.