Hello, I’m new to Unity and I’m trying to build a game for windows on my Macbook. The windows option doesn’t appear and the tutorials I’ve seen are telling me to use the Unity Download assistant but I think I deleted it when I downloaded Unity. How can I download the files missing and how do I install them? Thank you! 
you want to deploy to standalone or to universal windows platform? for universal windows platform as said here
https://unity3d.com/es/partners/microsoft/porting-guides
and if you want to build standalone you will be building towards mac