To allocate leave types for employees in bulk: 

Go to Payroll Settings >> Leaves menu >> click on Allocate Leaves link

Select Name of the leave and Location from drop down, this action will fetch all employees list based on configuration of leave type

Once employees list is fetched, click on Save button to save the details

To allocate leave types employee-wise:

Go to Employees menu >> Master tab

Search & double click on selected employee record

In Leave Details tab, select the leave types and save the same.