Alright, so you've made a FANDOM account, and are ready to add a page, or edit one!
It all starts with adding a page. Whether you do it or someone else, it the start. Once you do this (and name it) you can write everything you know about the character. See Guide for Beginners for help with non-canon and canon, but we want everything possible on that page. For instance, we don't want the F-11D blaster rifle to simply have history, but also the manufacturer, the army that used it, and whoever used it. Infoboxes help with this as well, for guns use Infobox:Weapon.
Once you have written down the information, then you can begin organizing it. First, you make the main section, which entails the overview of the character. Then, you will do the Description, History, Behind the Scenes, Appearances, and Sources (that is the general order, some sections may be omitted). Some headers are also possible, for example the ISD Inflictor has a section about it's known crew.
CATEGORIES! They can be one of the most helpful browsing tools to use, and connect related articles in a very handy web. You will need to add these at the end of your edit. Some categories that need to be on every article that applies are: Prequel, Original, or Sequel Trilogy, and Canon and Non-canon (only use when applicable). Other ideas are Galactic Republic, First Order, Imperial Army, and Weapons.
Spelling and Grammar
Your spelling should be good, but no, the wikia gods will not strike you down if it isn't (that's what admins are for, right?). The article should be written in a intelligible way, but that will be ironed out over time. You really shouldn't worry to hard about this right off the bat if you aren't into that kind of thing. Do your best, you won't be judged, I promise.