The category is used to separate videos. Videos can be listed under different categories - in other words products. The categories can be made of products and it is used to list the videos easily.
From the admin menu, go to catalog/opencartplayer, you should see 'category' tab, you need to add categories.
From the Category tab, click insert to open category form for adding new category.
Category Name is required to create category.
If you check publish, you can use that category in videos' settings then click save button.
If you need, You can add, update and delete the categories.