From the applicants list, select one or more applicants by marking the check box next to the applicant’s name.  Click the More button, and select Add Tag.  Enter the desired word or phrase in the text box.  Click the Done button to save.

From the applicant details page, enter the desired tag or tags into the Tag box.  Type the word or phrase that you wish to use as a tag in the box and hit enter to save the tag.  

A new feature that was added with this system upgrade was the ability to add multiple tags to a single applicant.