[mesa-users] activation command not recognized

[Blake.R.Mackall at williams.edu]

Dear MESA staff,

When i type the command to download MESA into the terminal on my macbook air the terminal says "command not recognized." I am fairly sure I've downloaded every prerequisite I need. I'm trying to get it up and running for the pre-school material for the MESA summer course. Thanks for your help.

Sincerely, 
Blake Mackall