Can someone show me how to get this third party plugin working?

I’m currently trying to get working with tern on emacs with company-mode. Unfortunately, despite following the instructions on that page, I haven’t been able to get GAS auto completion/documentation. Is there something else required to get 3rd party plugins working on a server?

(I’m a complete beginner regarding tern, sorry!)
Edit: I’m on Mac OS if that changes anything

I got this working.

Problem was that I wasn’t installing it globally with npm install -g tern-gas.