Just like many of the common Clojure web frameworks, noir is build on top of the ring framework. Ring produces Java servlets that are contained in .war files. Hosting providers know how to host war files. In general you use leiningen to produce a war file and give it to your hosting company through some manner of web interface (or by pushing it through git in the case of Heroku)
add the lein-ring
plugin to your project.clj's plugin section