Your demo video is very awesome - short, easy to follow, clear instructions! The library looks pretty cool!
To use within Clojure, just add c2 to your deps as usual and then
(ns your-ns
(:use [c2.core :only [unify!]]))
Use from within ClojureScript is pretty much the same.
Checkouthttps://github.com/lynaghk/cassowary-cljs-demo
for a rough demo.