In order to add your own unique keywords to the default categories, first navigate to the "Default categories" page on the left-hand side bar under the "Insights Customizations" subheading.
To begin editing, click on the edit button in the top right-hand corner.
You can then add which keyword you would like included within future analysis to any of the available categories by typing into the "Include" section of the available categories. Hit your "Enter" button in order to complete your entry.
Once you have finished inputting your desired keywords, click on the "Save" button in the top right-hand corner to save all of your work.