I think you are misunderstanding. Someone who is an absolute novice will not be able to do anything with the information given. Get Unren, click #1, open GIMP ...then what? I forget the term for experienced persons misunderstanding the difficulties of novices...
Following your instructions does not yield the same results on my screen. I can not find in any of the files the character images with all their detached pieces as you show in your image.
If you do not have a basic understanding of GIMP (or other image editor), how PNGs work, etc - you will need to practice. This is not the place for basic editing help - this thread is for sharing fan art and, as necessary, quick tips/suggestions.
But they are pretty much spot-on in their quick steps: Get
UnRen and move forward. Many of the characters' parts are already in position they need to be - if you use the parts from the same poses - when you pull them into your editor. This is why you see a lot of time is devoted in the progress chart to "posing" - this is what they are making sure of.
(see the following short video of piecing together a quick, minimal adjustment, scene):
If you need to learn how to do image editing, there are 10's of thousands of videos online to help you.
