To do this, get the ContentView object and add it what you need as params :.
$contentView = $event->getContentView();
Returns the location when applicable (viewing a location basically)
if ( $contentView->hasParameter( 'location' ) )
$location = $contentView->getParameter( 'location' );
Content is always available.
$content = $contentView->getParameter( 'content' );
Set your own variables that will be exposed in the template
The following will expose "foo" and "complex" variables in the view template.
$contentView->addParameters(
array(
'foo' => 'bar',
'complex' => $someObject
)
);