How can I add my Wordpress Site's template to my contribution page?
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As Jon says, you need to go to CMS Database Integration

www.example.com/wp-admin/admin.php?page=CiviCRM&amp;q=civicrm/admin/setting/uf&amp;reset=1

There you have the WordPress users table and the WordPress base page, I would suggest to create an empty page named CiviCRM - slug 'civicrm' and use that page as your base page in the menu mentioned above. 

This should be the default behaviour when you install Civi, as Civi automatically creates this page and sets it as the default base page, more info about this here.