This article explains how to manually build your plan's schedule of tasks. You will navigate to the Grid page. Refer to the next article for the steps how to publish a MS Project schedule of tasks.
Navigate to Schedule Grid
From the Portfolios page, open the Work Type and select Schedule.
Add New Tasks
See Create work items in the Work Plan Grid for instructions to add tasks.
View & Edit Tasks
See View and edit work items from the Work Plan Grid for instructions to edit tasks.