1.  You should have an published extract from OBIEE data using Tableau Desktop.  Refer to this step-by-step tutorial.  

Modifying Credential options for a Published Data Source

After you have published a data source / workbook to Tableau Server , follow these steps to edit the credentials for the Data Source if user credentials are not embedded

1. Navigate to your published Data Source.

Note: If you have published your Data Source without embedding credentials it will shown under Authentication Section as "Not embedded in connection".
2. Click on Connections Tab.
3. Click the  menu icon for the Data Source selected.

4. Click the  menu to edit the credentials for the published Data Source.
Note : If you have published the Data Source without embedding credentials user will be on the "Prompt user for password if needed" option.

5. To change the Data Source to embed password within select the  "Embedded password in connection" option radiobox .

6. Click "Change the password".

7. Enter the password in the text field for the specified user.
8. Click "Save" button to embed the password for the Data Source.