To allocate a promise (you must have the Resource Mgmt: Promise Unspecified Resources access grant and the parameter
ENABLE_PROMISE_RESOURCE_ALLOCATION must be enabled), do the following:
From the Resource Allocation Management page, click (in the Gantt view) or (in the Table view) next to the position to promise and select Promise.
A new line appears with Promise as the resource. The status defaults to soft-booked and the promised allocation defaults to the position's unmet demand. You can edit the promised allocation value as needed.
Note: You must click Save from the Table view of the Resource Allocation Management Page in order to save any promises you made. In the Gantt view, the promises you made are saved automatically.