Most pages in this wiki are added through "Forms". Always use the "Edit with form" tab in the upper right of the page to add information to the wiki - it makes it much easier!
Your Player Page contains information about you, the player. When you've made your player page, you'll see a section called "Player Characters" with a text box. Type in a character name, click the "Add or edit one of your characters" button, and add a player character. You may not be able to fill in all of the details in the form yet: don't worry. As you add other pages, you will be able to use more of the form. For example, you might be from a location in the Forgotten Realms that isn't available in the dropdown. Once you've used the Location form to add that location, it'll be available for selection in your character form. Note that you can only add player characters via your player page.
Non-player characters are referred to as "Supporting Cast" in the wiki. These are characters who could be used by anyone in a module or story - although you will forever be associated with them in the History page, and your name will also be associated with them.
Locations (or Canonical Locations) are places in the Forgotten Realms detailed by Wizards of the Coast. This wiki doesn't hold details about locations, but if you add a page with a location name (e.g. "Candlekeep") you can use the form to make a short page with a link to the Forgotten Realms wiki. When you've made a page for a location, you can then select that location in other forms - for example, adding it as a home for your Player Character.
Adventuring Groups are the traditional party of player characters that you'd see in a tabletop game. When you've made an Adventuring Group, you can then go back to a page for your character, click "Edit with Form", and now you can choose the Adventuring Group you have just added as your character's group.
Organisations are larger than Adventuring Groups - they may span one or more countries. The Harpers, the Lords Alliance, the Zhentarim, and the Red Wizards of Thay are all Organisations. Traditional computer game guilds that exist in character (such as the Mythweavers!) are also Organisations.
Now you've added a Player Character and some other content, go look at the network graph on your Player Page.
Modules (Foundries in Neverwinter Online, Modules in Sword Coast Legends) are content created by players. You can add them to the wiki, and even use the wiki to plan them. You can watch this video for more details on how to plan with the wiki.
Module Areas can be added to a module you've already created via that module's page. Module Areas have some properties that help you plan how to use them to tell a story, such as Tension. You can find more details in the Module Creation tutorial.
Module Reviews can be added for any module that exists on the wiki. These are done in a special page that is connected to your player page - this is in order to prevent other people from editing your reviews. When you're on your Module Review page, click "Edit with Form" to start adding reviews.
Campaigns are sets of modules that have something in common - perhaps a plot arc involving a draconic menace, perhaps the tale of redemption of an implacable foe of your guild.
Stories are the reason for the existence of the Mythweavers guild, and on this wiki they are what you'd expect: fantastical stories of adventure, of intrigue, of romance, or of the brutal and vicious slaughter of entire humanoid tribes. When you've added a story to the wiki, you can then edit your player character to indicate that he or she or it was involved with the story: if other people do the same, you'll start to see whole webs of social networks spring up between player characters. You can also add start and end dates to stories, which means they'll appear on the timeline. The current year is 1489 Dale Reckoning.
Events are single incidents, perhaps the time your adventurer stood fast on a bridge to let their companions get to safety, or the night your guild swooped down on its enemies and murdered them in cold blood. An event can be declared to be part of a story, and events also have dates and can appear on the timeline.