This feature enables you to forecast fees and resources (hours) for a period estimated in the Tasks/Stages/Phases screen. When you provide the estimated Start date and End date of a Task, Job Forecast will disperse the estimated fees and hours within the given period on a monthly basis. You can then edit them and forecast the resources in a way that suits your cash flow. You can even forecast the Subtask resources for each Task.
Getting started with your invoicing normally starts with a few reports to see who you are invoicing and for how much. This can then be checked with job (project) managers to confirm they are ready to invoice the clients and if they are happy with the amounts.
There are two basic reports that can get you going. Unbilled Work Quick Summary and Timesheet Entries.