"insert the structure [[BLOG_CONTENT]]
blog pages are saved in the blog folder, and you can also assign each its own template"

I don't understand what this means. Where, how do i "insert" that?
I tried simple linking to the test blog pages but it only works if i change the .txt into .html, and there seems to be no way to add the template.

Let's say, i want a subpage in my main navigation that says "blog". and then I want that subpage to have links to blog entries 1, 2, 3, 4.
I also want them to use the templates.
How do i do that?