Adding category and tags is very easy. I will first show you how to add a categories and then tag. In the picture below on the left hand side there is a panel with six tabs, one of those options begin categories and tags. Click on the categories and tags tab and then click add new category. Type in your category name and boom! You have a category now. Now that you have you can add a tag. Once again click the category and tag tab and click in the box below the word TAGS, add your tag (can be whatever you want it to be) and then press enter, and ka-boom you now have a tag.