To add an appointment using the Weekly Appointments window, do the following:
Click the left mouse button in the day that you wish to add the appointment, making sure that you click below the last appointment.
Now start typing the description of the appointment. When you have entered the description, press Enter to save your changes or Esc to discard your changes.
The duration of the appointment will be set to 30 minutes. The appointment start time will be set to the earliest time that you are available, after the start of the working day. For example, if you add an appointment on a Wednesday and the working day is set to start at 09:30 but you already have a 1 hour appointment at 9:45am then the new appointment will be added at 10:45am.
Another way of adding an appointment is to specify the start time and duration of the appointment as you add it. This can be done in the following way:
Click the left mouse button in the day that you wish to add the appointment.
Press the Insert key. The Appointment property sheet is displayed with the start date set to the selected day.
Specify the start time and duration and specify a description for the appointment. Press OK to save your changes.
Alternatively you can use the 
button to add a new appointment to the Weekly Appointments view. This will bring up the Appointment property sheet. The start date will be set to the
current date. Change the date, time and duration to the required values, specify a description for the appointment and press OK to save your changes.