Hi Wanda -
When you say the tasks are not editable, is that on the Project Plan or on the Tasks tab on the Requirement? Either way, your team members should be able to update the Estimated Hours, and then the Tasks will roll up both on the Requirement and on the Project Plan.
You can split a Requirement into multiple Tasks either on the Project Plan or the Requirements Task tab. Each task can be assigned to a team member.
If you are working from the Project Plan, just add a Project Plan Task and link the Requirement to it. Then under that task, add some sub-tasks - when you indent them, they are automatically linked to the Requirement above. Assign the tasks and your team members can put their estimates on the task. When you save the Project Plan, the hours on the task are added up and posted to the Requirement.
The same thing should happen when you work from the Requirement; on the Tasks tab, you can add Tasks, select the Project Plan and location for the tasks. The estimates on the tasks get rolled up to the Requirement and to the Project Plan.
If that's not what's going on, then maybe we need to talk to the Support Team so we can look at your specific Project Plan and Requirements.
Thanks!