greetings the files to download depend on which version of blitzmax you are running. are you on the latest? if so you will want to download the files from [a href=http://www.gprogs.com/forum/viewtopic.php?id=261]here[/a]. please read the directions on the download page for installation.
as for documentation there is no real documentation. the mod was designed to be as close to the C++ Irrlicht API as possible. there are a few exceptions to this due to BMAX not having method overloading and having to wrap up properties in get/set methods. so in general the differences are:
a) if there are overloads for a method the methods in the mod will start with the same name but have a bit longer name to make them unique. examine the mod files until you get a hang of my naming conventions.
b) anything that is exposed through a property is wrapped up in get/set methods. the name is usually getPropertyName()
since the mods are so close to the API i rely on folks using the API documentation from Irrlicht. the samples from Irrlicht have been converted and are available for download (at the same link above). i would highly recommend these as they are a great starting point. another good thing is that you can port code samples from the Irrlicht website over pretty easily and also get help on their forums (just be sure to follow their posting rules or they get nasty).
hope this helps you get started. feel free to ask questions here as much as you like.