Task labels are a personal way of keeping track of tasks and categorizing what needs to be done. Labels are visible to you only, so the labels you add to your tasks cannot be seen by your team members.
You'll find the task label field at the bottom of the task creation box. From here, you can select from existing labels or create a new one by simply typing it into the box.
You can manage your task labels from your Tasks page, available from the top blue bar in Podio. From here you can delete labels you no longer wish to use, or use the color picker to the left of each label to designate a color for that label.