First of all download Yii Booster latest end user bundle from here.

Download it, unpack its contents to some directory inside your web application. Its recomended to unpack it to the extensions directory. Rename the folder from yiibooster-<version_number> to just yiibooster for convenience.

Then we need to configure it. Add below line before return array

before return array

Inside components array add:

'bootstrap' => array(
    'class' => 'booster.components.Booster',
),

Then preload the yii booster by adding below snippet in the config preload section

'preload' => array(
    ... probably other preloaded components ...
    'bootstrap'
),