Change Single Column Joomla 1.5 for first Instalation

How to change Two Column to Single Column Joomla 1.5 for first Instalation?

1. Login to administrator
2. Klik Menus
3. Klik Main Menu and choose "Home" on the list of article
   
4. On right side, on column field change "2" to "1"
5. Click Save