Adding a tag is easy! You can add them when you first create your Hub before you publish it and you can add or delete tags any time. Here's what you do:
1. Click on the Hub article that you want to add tags to
2. Look on the right hand side of the Hub-you may have to scroll down a bit- and you will see tags that you added and also suggested tags.
3. You can either add tags from the suggested tags or type in your own tags manually
Be careful not to put too many tags in your Hubs. Follow these 2 links to learn more about how to use tags:
I hope this helps!