Has anyone come across a tutorial to create documentation for functions you create in Mathematica? I’m trying to organize some functions that I have written but so far I’m doing a terrible job. I would really like to have a file explicitly for the functions and one for the documentation and somehow add a path to the Mathematica documentation so that Mathematica can also search for it.
Take the documentation for the Sin function for instance:

When you click on the arrows it opens a notebook with information on the Sin function. I tried copying the contents of that notebook and pasting in a fresh notebook so that I can edit it but I can’t modify the contents.
I really like Mathematica’s format for the documentation and I would like to document my functions in the same way for future reference. Does any one know how to document functions the same way Mathematica does?
Perhaps this or this will be useful.