The theme uses modules to display posts and each module can display the post category tag. In the following image you can see how the tags look on a module in front-end:
Multiple categories case
If the post is included in more than one category the first category will be displayed. A specific category can be displayed only if you set it as a primary category in the post editing section.
Theme panel settings
To enable or disable the category tag on any module use the switches included in Theme Panel > Block Settings > Category tag on Modules/Blocks