I'm a new user. Not quite sure how to format things yet, but I guess you can talk here.
Maria-sama ga Miteru
Hey Gladiolus, thank you for reaching out to me and expressing an interest in contributing to Marimite! I'll start by addressing the easy things. When you sign a message, type two hyphens followed by four tildes (~). This is wiki code that will leave your "signature" and a link to your user and talk page. And it looks cool and professional!
Second, how would you like to contribute? Are you looking to help with translating or editing, or something else? If you would like to translate, there are several opportunities to do so. If you would like to edit, feel free to jump in and correct obvious errors such as improper punctuation (and placement) and spelling. Do keep in mind that edits across the project are varied, and a work in progress, so continuity of format standards may vary even across chapters. Volume 20 is a perfect example of this, and I am currently rebuilding it.
Translation, eh? Excellent, the extra help is appreciated! I'm sure you've seen enn_are(NR)(Talk) is currently finishing Volume 26, and has done a good chunk of the project. As I mentioned earlier, there are still some unfinished or missing volumes/chapters/parts dotting the whole project. I'm not sure what enn_are is planning to do next, but translations are pretty much a free-for-all. All you need to do is sign up for a chapter (or two, if you're feeling up to it) on the registration page. This bit is important; it helps avoid confusion, or two people accidentally working on the same thing. Generalized information regarding contributing to Baka-Tsuki as a whole can be found here, and is worth a read.
For this project, enn_are and I have been using the feedback thread on the forums for question/clarifications/answers. While I am most in favor of centralizing information and discussion, I don't mind communicating in whichever fashion you prefer. Project specific formatting was put forth by Seki when he first started translating, and we've pretty much kept to it. I do need to add our styling guidelines to that list, but you don't have to worry about adhering to it; that's my job once I get to it on the wiki. The major thing for you would be maintaining the translators' responsibilities, if only because I rely heavily on what is presented to me for editing.
So, that's pretty much it. If you have any more questions or concerns, feel free to ask me or enn_are (who would probably be the best to ask regarding project specific translation questions). If you'd like, I'd recommend joining the Discord server. Not only am I active there, but there are several other translators who could offer advice or help in a more timely manner (most of the time). I look forward to working with you! --Lunar Vitae (talk) 02:02, 2 June 2017 (CEST)
P.S.: I've only read up to Volume 28, so please don't spoil the story for me ;-;
I don't actually know where you could, as none are provided or available through Baka-Tsuki. I assumed most translators had the novels themselves.