Message templates "access denied"
your username has not got permission to Edit message template 

so please try to view - Drupal Access Control

Administer -&gt; Users and permissions -&gt; Permissions(access control)


where you will see the following role and try to enable for your user group 


  CiviCRM: edit message templates


If you don't have permission then please ask your admin or login to admin user and enable for specific user group 

refer to link https://book.civicrm.org/user/current/initial-set-up/permissions-and-access-control/

I guess this helps !!!