Colby & Michele Myers  put a @no space then start typing the name of who you're looking for.  Click on their mug when it pops up.

Now you've got it down and it looks like this question helped others as well.  Way to go Colby & Michele Myers !

Colby & Michele Myers - Type @, wait for the cartoon bubble to appear, type in a couple of characters of the first name and a list will appear.  Select the desired name as I did and the person is now tagged.

You can only tag someone that you are following or is in the thread of the blog. Using the @ sign gets the eligible names to come up.

Jill Murty, Realtor - Orange County, CA and John McCormack covered it for you. The name doesn't always need to be in the thread but if you haven't previously tagged them they won't show on the list.

You received a correct answer. 

Be careful not to overuse tagging.

John McCormack is exactly right.  I think they have to be on the thread or be someone you've previously tagged to be an option on the drop down menu.

Use the @

Use the @symbol

You can't go wrong if John McCormack gave you the answer

Okaaaayyyy I understand now how to do it ... but what does it mean?  what does it do?

Colby & Michele Myers 

Good luck,

Sam

I usually type their name, Colby & Michele Myers when writing a comment or answer.