You can easily add tags to wiki pages and blog posts.
When adding tags, be aware of what tags are used in your wiki because tags are more effective when they aren't duplicated. For example, it is better to have a "ProjectX" tag rather than "ProjectX" and "Project X" tags. Review similar pages to see how they're tagged to get ideas for how to tag your page.
To view tags:
When viewing a wiki page or blog post, click Details.
If you're already viewing the details, the Details button is replaced by a Hide button.
Click the Tags link.
To add a tag:
While viewing a wiki page's or blog post's tags, click Add Tag (+).
Enter a tag in the field and click Add.
To remove a tag:
While viewing a wiki page's or blog post's tags, click Delete a Tag.
Click Delete next to the tag you want to delete.