I do not know what versions you are using but Tagalong version in that blog was 1.1 and is not the version you should be using . The article you reference that announced the version release is over 3 years old, that isn’t current documentation. It was accurate three years ago. The current docs site is here
Have you updated and are you using Power? if so you should see a Categories tab , Have you installed the Experience add-on? What versions of what are you using ? Please follow the Posting guidelines so we can better assist you.
The documentation for the Legend for icon array etc is here,
Iconarray and categories