PatternSkin.zip in your twiki installation directory
pattern and you still don't see the layout as on the screenshot, a few settings in may have been disabled.
Check these variables here: 
   * %SYSTEMWEB%.PatternSkin settings:
      * Set TWIKILAYOUTURL = %PUBURLPATH%/%SYSTEMWEB%/PatternSkin/layout.css
      * Set TWIKISTYLEURL = %PUBURLPATH%/%SYSTEMWEB%/PatternSkin/style.css
      * Set TWIKICOLORSURL = %PUBURLPATH%/%SYSTEMWEB%/PatternSkin/colors.css
NOTE: customization of these values should be done in Main.TWikiPreferences
If this still does not work, contact the administrator who installs skins.
For further troubleshooting and feedback, go to TWiki:Plugins/PatternSkinDev| Skin Author: |  TWiki:Main.ArthurClemens | 
| Copyright: |  © 2004-2008 TWiki:Main.ArthurClemens © 2008-2013 TWiki:Main.PeterThoeny © 2004-2013 TWiki:TWiki.TWikiContributor  | 
| License: |  GPL (GNU General Public License | 
| Description: | TWiki's base skin; CSS based, flexible and W3C-compliant | 
| Screenshot: |     | 
| Preview: | Preview with this skin | 
| Base Name: | pattern | 
| Skin Version: | 2013-01-10 | 
| History: | |
| 2013-01-10: |  TWikibug:Item7088 | 
| 2012-10-23: |  TWikibug:Item7006 | 
| 2012-03-23: |  TWikibug:Item6834 | 
| 2012-01-19: |  TWikibug:Item6838 | 
| 2012-01-13: |  TWikibug:Item6832 | 
| 2011-07-28: |  TWikibug:Item6780 | 
| 2011-07-27: |  TWikibug:Item6779 | 
| 2011-06-11: |  TWikibug:Item6209 | 
| 2011-05-18: |  TWikibug:Item6682 | 
| 2011-01-03: |  TWikibug:Item6628 | 
| 2010-12-20: |  TWikibug:Item6622 | 
| 2010-11-25: |  TWikibug:Item6608 | 
| 2010-09-24: |  TWikibug:Item6544 | 
| 2010-07-03: |  TWikibug:Item6514 | 
| 2010-06-19: |  TWikibug:Item6499 | 
| 2010-06-12: |  TWikibug:Item5335Main.FirstLast or [[Main.Firstlast][Firstlast]]; force-linking user name in topic info in case NOAUTOLINK set -- TWiki:Main/PeterThoeny | 
| 2010-05-25: |  TWikibug:Item6453 | 
| 2010-04-28: |  TWikibug:Item6416 | 
| 03 Aug 2008: | v.3.0.1 - TWiki 4.2.1 (Edinburgh) RELEASE VERSION | 
| 13 Jul 2007: | v.3.0.0 - TWiki 4.2.0 (Edinburgh) RELEASE VERSION | 
| 15 Jan 2006: | v.2.0.6 - TWiki 4.1.0 (Edinburgh) RELEASE VERSION | 
| 26 Sep 2006: | v.2.0.5 - Fixed form background colors | 
| 22 Jul 2006: | v.2.0.4 - Refactored info in colors.css; fixed textarea color | 
| 26 Jun 2006: | v.2.0.3 - TWiki 4.0.3 (Dakar) RELEASE VERSION | 
| 31 Jan 2006: | v.2.0.0 - TWiki 4.0.0 (Dakar) RELEASE VERSION | 
| 28 Aug 2004: | v.1.0.9 - TWiki 3.0 (Cairo) RELEASE VERSION | 
| 08 Aug 2004: | Initial version (v1.0.0) | 
| Dependencies: |  TWiki:Plugins/TwistyContrib | 
| Skin Home: |  http://TWiki.org/cgi-bin/view/Plugins/PatternSkin | 
| Feedback: |  http://TWiki.org/cgi-bin/view/Plugins/PatternSkinDev | 
| Download: |  http://TWiki.org/cgi-bin/view/Plugins/PatternSkin |