Create it
Projects → New project.
Break it into stages
Open the project and go to Stages → + Add stage. Each stage takes a planned cost, a planned revenue and a progress percentage.
Stages are what make Overall progress and Budget used mean anything. Without them a project is one number that moves when somebody remembers to move it.
Where the real numbers come from
You do not type actual cost. It arrives on its own:
The Overview section then shows Billed, Collected, Yet to bill and Not yet invoiced against your contract, and margin against your budget. Over budget by appears in red the moment it happens rather than at the end.
Time and subcontractors
+ Add entry logs hours or a fixed amount per stage, against a worker or a vendor. When you are ready to pay a subcontractor, generate a bill from what is logged instead of retyping it.
Billing the client
From the project's Invoices section, or from an estimate: a stage-level estimate can be progress-invoiced as each stage completes, so you bill what is finished rather than the whole job.