diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 015ff53d..bcafd746 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -58,10 +58,10 @@ the CSS files will be overwritten when compiling the stylus files. Instead, you
 [stylus files](https://github.com/azerupi/mdBook/tree/master/src/theme/stylus) and regenerate the CSS.
 
 For this to work, you first need [Node and NPM](https://nodejs.org/en/) installed on your machine.
-Then run the following inside of the mdBook directory:
+Then run the following command to install both [stylus](http://stylus-lang.com/) and [nib](https://tj.github.io/nib/), you might need `sudo` to install successfully.
 
 ```
-npm install
+npm install -g stylus nib
 ```
 
 When that finished, you can simply regenerate the CSS files by building mdBook with the following command: