Mohamed A. answered 04/06/20
Project Manager, PMP Certified and Construction Management Consultant
All of the above steps are required to create the project time plan (Schedule).
First, you breakdown the whole project into WBS's depending on the way you handle the project. Then, develop the activities (tasks) associated with each WBS. Then, you determine the activity duration. Then create the relationships (dependencies) between all activities. Finally, Run the project and see your critical path and do some fine tuning before performing analysis.
All of the above steps are for (Non resource allocated) Schedule. If you want to build a Resource Allocated Schedule, you have to add "Assign Resources to activities" after developing the activities.