To make an appointment while checking your email, click on the "office button" located on the top-left corner of your email screen.
Once there, click on the "Appointment" option from the right portion of the drop-down menu screen.
From there you will be prompted to add infromation on the appointment.
Click "Save and Close" once you are done with the process of creating an appointment.
You also have the option to invite attendees by selecting "Invite Attendees" and sending the email.