I have enabled tagging. Now here's the thing. In order for the tagging to "work" you're going to need to go to the edit settings in your account. Turn everything you want on to instant and check what you want. There should be a thing for "tagging" 

Now to tag in the shoutbox you will need to put in "@username" sometimes user names are different. Like if you wanted to tag someone like Zari Shine you put down
@zari

So when you tag someone it should look like this

Zari Shine
Trase
Nakiya
Vierra

Have fun!