1. Login to your WordPress admin dashboard.
2. Under the dashboard menu, hover your mouse on Posts and then click on Categories.

3.Enter the following details in Add New Category:
  Name: Enter your category name such as Computer.
  Slug: Enter a slug name or leave this as it is.
Click on Add New Category

4. New Category Added Successfully.

How to Remove a New Category.
1. Login to your WordPress admin dashboard.
2. Under the dashboard menu, hover your mouse on Posts and then click on Categories.

3.On the right side, you can see a list of categories. Hover your mouse on a category you wish to remove, and a few options will appear. Click on the Delete option. The confirmation option will appear. Click on OK.

Done:-