There are three kinds of writing that fall under "theos logos":
1. Record-keeping 2. Transformative writing 3. Creative writing
and each of these has mundane as well as magical essence. (There are non-theos writing motivations as well, such as writing purely for money or amusement, but to write purely and entirely for those reasons is rare.)
Record-keeping is the most straightforward type of storytelling. It's simply a matter of writing down what happened. When your teachers tell you to "write what you know", this is where you end up, and even journalism can fit in this category.
The mystical aspect of record-keeping is the act of channelling. This can also fall under the description of soulbonding, musing, or some kinds of multiplicity. When someone comes to you and says "this is my story", and you write it, that's channelling. Sometimes it's said that this has no creativity to it -- or at least not in comparison with other kinds of writing. That's drek, however. There's an artform to telling a story, regardless of whether it was told to you at first or not. (There were many, many stories about the Trojan War. The Iliad survived.) There can, in fact, be a great deal of duty attached to a channeller, especially one who is charged with relaying the stories of dead planets, forgotten races, and other such dusty muses.
Transformative writing starts with simplistic actions -- self insertion fanfic, wish fulfillment fantasies, and so on. It is writing what we want to see, rather than what is.
Magically, transformative writing is all about understanding that the world we live in is also a story, and that we as characters can influence the author as surely as those who speak to the record-keeper influence their own stories. Write yourself a better life, a girlfriend, everything you want. This is similar to chaos magic, in that both encourage the use of symbols as a focus for energy. (I'm still looking at sigils and narratives, Grant Morrison stuff.)
Creative writing (and that needs a better term, really) is the act of creating a world by writing about it: playing God, so to speak. The best description of this I've seen is in the Myst games and their related material, where the philosophical debate about the existence of the worlds being written is actually part of the plot.
You have spent six weeks now, learning how to copy a number of basic D'ni words and have discovered just how complex and beautiful a script it is. But those characters also mean something, Atrus. Something much more than you've previously understood. And not just in this world. They were developed over tens of thousands of years for a specific task -- that of describing Ages... of creating other worlds. They are not like the words you and I speak casually, nor can they be used so in the books. Writing -- D'ni Writing -- is not merely an Art, it is a science. The science of precise description...
When we begin, there is nothing. It is... uncreated. But as soon as the first word is written -- just as soon as that first character is completed, the last stroke set down upon the page -- then a link is set up to that newly created world, a bridge established... Ahead lies an immense amount of hard work. Every aspect of the Age must be described, each new element fitted in.
-- pp 171-174
What if they weren't so much making those worlds as linking to pre-existing possibilities?
At first he had dismissed the notion as a foolish one. Of course they created these worlds. They had to be! How else would they come into being in such precise and predictable forms? Besides, it was simply not possible that an infinite supply of different worlds existed out there, waiting to be tapped. Yet the more he'd thought about it, the more he had come to question his father's simpler explanation.
-- pp 203-204
All writing is creative, but some of it is more creative than others. Creating a world, discovering its gods, and getting to know its inhabitants is a way to draw closer to deity in your own life.
There are other ways to use writing as a stepstool to the divine, but these are the three I know best. If you've got suggestions too, let me know in the comments.