Appointments can be either scheduled from the or from the details page of the job you want to schedule an appointment for.
To get to your schedule, go to the Schedule page by clicking the Schedule button on the tab navigation bar. This will take you to the schedule screen, which will show the schedule for the next two weeks. If your appointment is within the next two weeks, find the date and click the plus button to the right of the date. If the appointment is more than two weeks out, you can click the Your Calendar button on the top of the screen, choose the date, and then click Schedule an Appointment.
On the Schedule an appointment screen, choose how long it will take, the start time, and add any related notes you may want to keep up with. Next select the job it's for. It can either be an existing job or a new one. When finished, press Schedule this Appointment. If it was for a new job, you'll be taken to the page for creating a job, otherwise the appointment will be scheduled for the chosen job.
You can also add an appointment directly from the job's details page. Find your job from the Jobs page,click it, and then click the blue popup menu button on the upper right and choose Schedule an Appointment. The appointment's date defaults to the current date, but you can change it by pressing Choose another date and picking the date from the calendar. Either way, choose the duration, start time, and optionally add any notes. Press the Schedule this Appointment button to finish and create the appointment.