How to use github extentions?

I hate to be that guy, but I just can’t figure it out.
How do I make the github extentions work with chrome?

Context is lacking with this one.
If you at least link it then perhaps I can guide you.

Is it different from each userscript?
Well, I guess I am trying to install this one
This link is from the readme provided on the page you linked (displayed at bottom of page). The “greasyfork” link contains an “install this userscript” button, which provides an explanation of how to use greasemonkey.

greasemonkey (and it’s chrome extension counterpart) inject arbitrary javascript code into webpages, thus creating the addon as a greasemonkey extension allowed the creator to skip several tedious steps in browser integration (making a standalone extension) and increased its portability.

Oh… I thought it was an alternative way to install the userscript…
Now I feel like an idiot

Don’t feel bad, it’s actually more surprising when regular computer users are familiar with software and computer engineering practices/standards.