An Overview and Introduction - An overview of IceFrog and introduction to converting your site to use IceFrog.
IceFrog Input (ifi) Syntax - ifi files are the basis of your web site. You'll typically have one ifi file for each resulting HTML page you want. Here is the syntax for the ifi files.
IceFrog Extensions to Template Toolkit - IceFrog is built on top of Template Toolkit, so for information on writing templates your best source is the official Template Toolkit documentation. You will want to check out the IceFrog Extensions to Template Toolkit for details on what IceFrog has changed and added.
With that in mind, for information on the syntax of template files, check out the official Template Toolkit Manual. In particular, the following sections are likely to be useful: