To create the initial set of tables, you need another tool. If you're doing this yourself, you can use Oracle SQL Developer (link below), and if in your organization this is something that is typically done by your DBA, she might already have another tools she prefers for the job.
http://www.oracle.com/technetwork/developer-tools/sql-developer/downloads/index.htmlAnd of course, you'll let us know if you're having any trouble with this.
Alex
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