The table is saved. Choose the dashboard it goes on: it becomes the first object there and the dashboard's editor opens.
The table is not loaded as long as no filter is set. Instead it offers to load the default filters, or to compute it anyway.
Set by the "Load default filters" button of a compute-heavy table. Without a date range here, the default filters of the dashboard are used.
Drag dimensions into Rows and Columns and metrics into Values. The order inside a zone is the drill-down order. Each value has its own aggregation (SUM/AVG/MIN/MAX) and number format.