Hello Sandyss,
to find your section id go to the section and look at the url see below
How do I find my section id?
When clicking on your section you should see something like this:
http://www.domain.com/content.php?11
The number after ? in this case 11 is your section id.
Can I enter more than one section id?
Yes simply change $section = '11' to something like $section='11, 12, 13'