To plan for a vacant position in HCP, you create a To Be Hired (TBH) employee to serve as a placeholder for the compensation expense associated with your planned employee.
From the Monthly Pay Rate tab on the Manage Existing Employees and Job Codes form, right-click on the first column and select Manage TBD -> Add TBH. Select the DeptID (defaults to the DeptID in the right-clicked row), TBH #, Job Code, Monthly Pay Rate, Start Year, Month and End Year /Month and any Comments.
Once the TBH is added you will need to add a TBH Distribution by right-clicking over the new TBH on the Monthly Pay Rate tab and selecting Manage TBH / Add TBH Distribution.
Once the actual employee is hired, you can then assign that employee to the To Be Hired employee in the compensation plan. See To Be Hired Employees for detailed instructions.