Good day, 

To add unpaid leave please click on:
Payroll > Payslip > ‘+’ next to earnings > select "unpaid leave" > enter the number of days > select days and not hours in the 2nd block.

Please note that this is going to be a negative earning

sorry, I did not mention that this is (negative) -7 days sick leave.  so I need to deduct 7 days sick leave as the employee took 37 days sick leave in the 30 days cycle(3years)

Hi, because the employee took 37 days sick leave. So the 7 days will then fall under Unpaid Leave. 
When you add the Unpaid Leave line under Earnings, and you enter in the 7 days, you will see that it is a negative amount, that will be deducted from the Employees Salary.