Oracle Database Management - Oracle 10g Database Administration Concepts and Implementation Made Simple - page 240

Managing Tablespaces/DataFiles
Under Administration tab, there is “Tablespaces” link as shown
in Figure 9-5. This link will not only provide you the information
about the tablespaces currently in the database but also helps you
to add/delete data files or create new tablespaces etc. all with a
few clicks. No need to type or memories SQL statements.
Figure 9-5: Manage Tablespaces in your Oracle database using
Tablespaces link.