When an employee applies for leave his Supervisor will receive a mail with a link to the leave list and upon clicking on that link either the Supervisor or the Admin can approve, reject or cancel the leave.
Step 1 - Navigate to the leave list/Leave Request by either clicking the link in the email or use the main menu (Leave>Leave List)
Step 2 - If you used the Menu instead of the link in the email, Search the list based on the employee name. Make sure to select "All" checkbox in the "Show Leave with Status" section.
Step 3 - For each record, select the action from the drop-down list and click Save.
if a leave request came for multiple days, it will be bundled and will be shown as one record. Because of that, the action taken will be applicable to all days. If you want different actions taken for different days, click the 
Detail button. It will expand the request and allows you to take different actions for each day.
Click 
Comment button to add a comment to your action.