Before you can add labels to your appointments, you'll need to create one first. To create a Label do the following:
Go to the Settings > Labels page.
Click the orange + sign to create your desired label.
Enter the label name. (This is internal only and not visible to clients.)
Optional: Check the "Stop Reminders" box in the edit mode of the label to prevent appointments using this label from sending reminders. (Useful for labels such as 'canceled, etc'. Checking this box is not required.)
Click the Save button to keep your changes.
Once your Label has been created, you can now add it to an appointment as needed. To add your new Label to an appointment, follow the instructions below:
Go to the New tab in your account to access the appointment form.
At the bottom of the appointment form, select a label from the 'Label' dropdown.
Click the Save button at the bottom of the appointment form to keep all changes.