Not sure that answers the full question..
TBH, it's not something SWC can answer, though -- we're essentially a fansite and don't receive profit, so we're pretty much the same idea as fanfiction, which isn't something that action is taken against.
But if you want to actually publish a book or ebook, that no longer qualifies as not-for-profit. I read an intro to one of the SW novels ages ago where the author posted a quick explanation about how to get started publishing SW material, and I don't remember the details anymore but it isn't a simple thing since all published SW materials need to conform to specific standards and need to be approved. You'd need to google more of that if you ultimately are interested in being published.
As a writer for the Combine, as Elijah points out, you can submit descriptions, contribute to the Holocron
(which most players start by creating a page for their own character), participating in White Scenarios or in the Meeting Hall or even in IRC roleplaying in #swc-ic. Many faction forums offer roleplaying opportunities. The White Scenario team also offers pre-scenario training
, which is an introduction to good and consistent writing (as well as scenario-specific bits like avoiding godmoding). You can also move on to writing GNS posts for your faction or with an information faction that has an emphasis on GNS posts (though Veritas Press is the only group I've seen that will write GNS posts for others; perhaps if you investigate that route further you can find more opportunities as well).
Or if you wish to improve writing in general, you can always start with fanfiction and see if you can get some decent critiques for it. People sometimes post links to their stuff in the forums and I've seen it in the -members channel lately, so I guess you can probably track down other players to swap feedback with.