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You can start by going in to admin>>templates. After you have cloned the default, you can then save changes you make. In your new copy of the template, go to the news templates and edit your files there to your likeing. Once you open them, you will see how things are currently laid out and then you can make new tables, rearrange things or what ever it is you would like to do.
Once completed, go to the system admin>>preferences and set your cloned template as the default in order to see your changes.
Hope this helps.