I am new to this comunity and I am enjoying getting the badges. It is fun helping people.
Though what is a Tag Wiki? I have no idea.
I assume the badges you are asking in regards to are the Tag Editor and Research Assistant badges. Tag wikis are also known as the Tag Info, and can be found by going to
http://gaming.stackexchange.com/tags/[tag-name]/info. At the bottom of the page there is a button that says "Edit Tag Info" which you can use to edit the wiki.
Note: any edit you make on these will be sent to a review queue to be approved/disapproved before the edit goes into effect (if you have over 20,000 rep, you can edit them without a review).