After creating a Blog category vocabulary, you will now need to define categories like Technology, Sport or Politics. These are called terms.

To view or manage the terms of each vocabulary, click on its list terms link. On the list terms page you can edit each term by clicking the edit link. Now, on the edit term page you have several kinds of choices.

Step 1: Assign your term a name.

Step 2: Choosing the term's "parent", if this term is a subterm of another term.

Step 3: Select term to be related (you can select multiple terms by using the standard conventions of your operating system, like shift-click and control-click).

Step 4: List synonyms for your term.

Step 5: Add weight for term.

Step 6: Finally click on save.

This is screenshot:

Master Drupal in 7 hours - Advanced Customization - Create category - Creating terms_01

Continue this step to create more terms like Sport, Politics, Economy and so on.

Now everytime you write a blog article, you can choose the category that it belongs to, like this screenshot.

Master Drupal in 7 hours - Advanced Customization - Create category - Creating terms_02