Installation and brushes.
This needs adding to the head of the blog html:
*Design -> Edit html -> under the "<head>" tag
Add this when you want to add code:
*You will need to switch to the HTML view when editing the post in order to add the "<pre>" tag
<pre class="brush: brush_name"> Your script here </pre>*brush_name can be js,perl,as3,etc. For a complete list see: brushes
Just to clarify the 3 files are, shCore.js, shLegacy.js and shAutoloader.js