There are there are three different privileges surrounding tags, granted at different reputation levels published here.
Different Stack Exchange communities grant privileges at different levels, but currently for ServerFault they are as follows:
300 create tags - Add new tags to the site
2500 create tag synonyms - Decide which tags have the same meaning as others
5000 approve tag wiki edits - Approve edits to tag wikis made by regular users
Not only tag related:
- 20.000 trusted user - Expanded editing, deletion and undeletion privileges (also removes the review requirement for tag wiki edits)
Which means that at your 400+ reputation level you have sufficient rep to create new tags.
There is nothing immediately obvious in the manual at which reputation level you can start editing tag wiki's, but maybe that privilege is included with the edit community wiki privilege, granted at 100 points.
As longs as you have less than 20000 reputation, your tag wiki will be peer reviewed before it is published
The number of active reviewers on ServerFault is quite low (I'm no longer one of them either) so edits might be pending for quite a long time.
For instance the relatively new SLES15 tag https://serverfault.com/tags/sles15/info currently shows
Once I hit the Edit Pending button I see the review option and your suggested edit:
in the "tags" context when hovering over a tag, there is a link like "improve this tag" that allows me to edit the "tag wiki". However when a tag already has some description, there is no such link, and I wonder how I could improve the description of such a tag.
There are two additional ingresses to edit tags.
Click on the tag and you get the "questions tagged [tag]" page
- The Improve tag info... link immediately brings you to the editor.
- The Learn more link shows you the tag wiki, where the Edit tag info button at the bottom will bring you to the same editor window.