After installation, there is a checklist that you should complete (e.g. http://example.org/civicrm/admin/configtask)
Some of the things needed for a first-time setupInstallation Checklist<ref>See also: https://hq.palantetech.coop/projects/commons/wiki/CiviCRM_launch_checklist</ref>:
<ol>
<li>Enable the CiviBartik theme, for Civi admin, and then immediately configure various blocks to NOT appear in that theme (remove everything from column two, so that you get a wide display)