When you open the Business Cube - Join Editor, you will see all the tables (including views) that have been added to the business cube when you create it. If you find that you require some extra tables to create joins, you can add them as follows:
Click the Done button to close the dialog. Then, all the selected tables/views will be shown in the right panel of the Join Editor window.
Now, you can define joins among the selected tables as required.
Tips:
 in the upper right corner of the table. To redisplay hidden tables, in the Business Cube - Join Editor window, click Table > Table Properties to show the Table Properties dialog, then move the hidden tables from the Hide Tables box to the Show Tables box (you can also use this dialog to hide tables without join relations).