Where to change backgrounds

I use “Home 7 – One Page Layout”, but I want to replace these scroll-over background images:

<div id=”av_section_3″ class=”avia-section main_color avia-section-large avia-no-shadow avia-full-stretch avia-builder-el-14 el_after_av_section container_wrap fullsize” style=”background-repeat: no-repeat; background-image: url(http://kriesi.at/themes/enfold/files/2013/04/photodune-757323-living-room-m.jpg); background-attachment: fixed; background-position: top left; “>

and

<div id=”av_section_6″ class=”avia-section main_color avia-section-large avia-no-shadow avia-full-stretch avia-builder-el-29 el_after_av_section container_wrap fullsize” style=”background-repeat: no-repeat; background-image: url(http://kriesi.at/themes/enfold/files/2013/06/tablet-1.jpg); background-attachment: fixed; background-position: top left; “>

Where can I do that, i don’t see these in options??

Regards Henk