In the Select Database Instances dialog box, click New... (or select an existing instance and click Edit...).
Enter the User Name with which to access the database (with SELECT_ANY_TABLE system privilege).
Enter the Password for the user entered.
Enter the TNS Host String. Note: The TNS Host String must match an entry in the tnsnames.ora file on the client system.
From the drop-down list for Mode, choose Standard or Limited Access. Note: Standard Access Mode is the default and you may proceed immediately. To use Limited Access Mode, the system must have the mode enabled and a specific account must be created. Click here for more information about Limited Access Mode.
Click the OK button to save the database specification.