I don't know How to modify this function.

Hi all
I want to add 2 inline ads. One add I added via theme in the first paragraph and second I have to modify this code to add a second ad in the 4th paragraph.
TAG DIV told me How to do that, http://screencast.com/t/KBSv3cT48IoI but I don’t Understand very much how to modify a theme.
Please can anyone help me.
Thank You Very Much
Sorry for my Bad Enlgish

Please can anyone help me ?

You can try to add this code:

// ads en otra posicion en post.
if ($content_part_index == 6){
$content_buffer .= td_global_blocks::get_instance(‘td_ad_box’)->render(array(‘spot_id’ => ‘custom_ad_1’));
}