Blog tags?

I installed the tags extension.

However I do not see how I would add “tags” to a blog.

Also from the instructions

Make a page to sit in /search/by-tag, and give it the “Tag Search”
pagetype.

is cryptic to me. I do not understand what they are trying to say.

I would like to construct a side bar which would contain all of tags and
counts allowing the user to select a tag and see all of the posts that
have that tag assigned.