Excited that Firebase\'s hosting is now out of beta. Trying to get going with with the firebase-tools package and I\'ve successfully installed it:
npm instal
This worked for me on Mac (same thing the others have been posting above, just for Mac):
go to your home folder in Finder (named after your user name, in my case "macbook")
press cmd+shift+dot (will reveal hidden files)
go the .npm-global/bin folder and copy its path (Finder menu -> View -> Show Path Bar, right click on the bin folder in the path bar -> "Copy 'bin' as Pathname")
open Terminal (by default the home folder) and go nano ~/.bash_profile
at the top of the file add export PATH=" (will look similar to this: export PATH="/Users/macbook/.npm-global/bin:$PATH")
save .bash_profile changes and restart Terminal, firebase command should work now