I just gained the "Edit Tag Wikis" privilege and went to edit the
z-index tag. It "has no wiki" and I would like to help create it, so I clicked the link.
What is meta?
- Any Stack Exchange user can ask a question
- The community provides support, votes on ideas, and reports bugs
- Your voice helps shape the way Stack Exchange operates
Since you fail on both counts, you can rule yourself out of being able to edit the tag wiki at this stage.
The new edit suggestion system allows you to suggest edits or new wikis for any tag.