An editor in a wiki can be almost anyone. In Open Politics, you can declare yourself an editor by adding a link to this page from your user page.
If the title sticks, you can wear it.

The OP learning hierarchy:

user > editor > senior editor --> chief editor

Editors are encouraged to learn the editor guidelines, which is the style manual for the wiki.

What do editors do?

Editors should know how to do all of the following:

Who do editors take orders from?

Editors don't take orders from anyone, but they will sometimes check the todo page and pitch in with tasks that need doing or are works in progress.

Does it pay?

No, but becoming a senior editor makes you eligible for tasks on the OP:todo list, which may be paying jobs.

How do I become an editor?

By studying the editor guidelines, becoming familiar with the wiki best practices.
When you feel confident enough to do so, add the title (and link) to your user page. If the title sticks it is yours.

Current Projects

Todo is a page which lists all the current projects and assignments that editors are working on.