By hand
In the admin
- Open Post settings in the editor, type a name under Tags and press Enter. A new name makes a new tag.
- Keep the most important tag first: it is the primary tag.
- As you type, the field offers the tags you already have. Remove one with its button.
- To tag many posts, tick them on the posts list, choose Tag, type the name and press Add tag.
- Filter the posts list by Tag to see what each one holds, or the posts without one.