Why wouldn't you be able to load it with notepad? It is, for all intents and purposes, nothing but a textfile with a different name.
The normal windows editor is able to open it - I've donme it many times - but sometimes messes up the file. It's better to use something like notepad++. And be it only for the highlighting

I just assume that you were able to copy the .brf, .dds, .txt files and so on to the right folders. And that you did so after creating a second M&B install, preferably by copying a clean and unaltered 1.01 install and renaming it to something like M&B with PL.
The OP and the 'guide' on page seven clearly states what you have to do here.
Now you open the module.ini and basically do what you'd have to do with any iother mod if you're going to add something to an existing module - adding the .brf files to the .ini.
I could just say "look up any instance where there's
load_ressource = name-of-a-brf-you-just-added-from-the-PL-download and rewrite it so, it says
load_mod_ressource = name-of-a-brf-you-just-added-from-the-PL-download", but I've got some sleep last night for a change, so yeah...
I'll write down what the OP and the post on page seven say, again.
Each of the following lines, i.e.
load_resource = materials
load_resource = map_tree_meshes
load_resource = tree_meshes
load_resource = xtree_meshes
load_resource = grass_meshes
load_resource = plant_meshes
load_resource = xtree_meshes_b
load_resource = terrain_borders
load_resource = tree_e_meshes
load_resource = xtree_meshes_c
load_resource = grass_meshes_b
has to be changes to
load_mod_ressource, e.g.
load_resource = materials to
load_mod_resource = materials.
This will tell the game to rather use the files in the module folder than the ones in the root folder.
And that's it.

Hardly difficult when even I got it right the first time around.