Click on the participant's profile you wish to add a category to

Click on "Add category" to create a new category

Add as many categories as needed by clicking again on "Add category"

Select the category you wish for this specific attendee.
You can add as many categories as needed to your participants

You will be able to see the category tab on the participant's profile.
You can do the same with all of your participants one by one.

Click on the edit pencil to edit the category name or delete the category

Click "Delete category" if you wish to delete the category

Now you know how to add categories to your participants

If you export the list of participants from this module you will see a column with the categories assigned to the participants

Add categories to your participants