Place yourself in a $PATH folder

I have a custom folder for little projects like my wiki-fetcher function. I have exported that folder into my $PATH.
You can check what exactly is in your $PATH by running
echo $PATH

Download the Leiningen script and save it (as plain text) in any $PATH folder

Here

Open another terminal

Run lein repl

First time will download the Clojure files. This is a one time event.

There you have it. Have fun.

Credit where credit is due. http://charlie.griefer.com/blog/2011/08/03/clojure-in-3-minutes/