This is the procedure I use for creating new projects with yiiframework:

Download latest code from http://www.yiiframework.com

cd ~/tmp
wget http://yii.googlecode.com/files/yii-1.1.5.r2654.tar.gz
tar xzvf yii-1.1.5.r2654.tar.gz

Create a new directory for the project:

mkdir ~/workspace/www/myproject
cp -R ~/tmp/yii-1.1.5.r2654/framework/ ~/workspace/www/myproject

Create an initial application skeleton:

cd ~/workspace/www/myproject
framework/yiic webapp public

Move application directory outside from webroot (for security reasons):

mv public/protected/ application

This is the final directory structure:

application  framework  public

Edit public/index.php and update new application location:

$config=dirname(__FILE__).'/../application/config/main.php';

Now point your web server webroot to ~/workspace/www/myproject and you should get a welcome page.