Below are some links that should help you on learning how to edit the wiki. The trickiest bit (I found) is creating the template if there isn't already one and you want to do something a bit different. Usually you can just copy and paste the format from a similar but if you're having trouble just give a shout on this thread.
Wikipedia Editing Cheatsheet
Manual of Style
To get started editing make sure your logged in (the Aeria games website and the wiki are connected so use your Aeria games login information) and hit the edit button either at the top of the page or on the right side of the page next to the intended category/object.
As for the Sprite Island information, yes that will be uploaded I knew I forgot to add something to that list. I started working on it a few days and hopefully I'll have the guide uploaded by the end of today~
I was able to access the edit function for the Mastery Guide on one of my alt accounts. The way I found to edit Masteries tables is to actually search the name of each table (which just brings up the table page itself) and you can edit it from there like here for example: Legendary Talents:Assassin
I think thats what you were referring too, sorry if I'm mistaken.