You will be able to add call manually from 
Global Data → Calls section
Click on the Calls tab and select "Add Call" button from the top right of the section
"Add New Call" popup will appear
Select Contact/Lead you would like to schedule calls with
Select the Event
Choose a Host by selecting any of the two options:
Round Robin → iClosed assigns a host according to the Event Priority or
Select Manually → and choose a Host from the drop down list
Click "Schedule call" and select time and date inside the calendar