Change Resource Planning Mode
The default resource planning mode - Project (formerly top-down) or Task (formerly bottom-up) is determined by your project category (your administrator can adjust the default using the self-service administration feature). You can select the planning mode when you create a project, but you can't change the mode once the project has been created (the setting is read-only). However, you can change the mode using the Re-Plan button from the staffing screen. Click Re-Plan and pick the appropriate radio button.