How do I use foreach to get content from a custom-field in multiple posts?

The custom fields I am using are from the plugin ACF (Advanced Custom Fields).

I finally looked at the ACF website, which I should have done originally, and found the function get_field can specify a post so here is the working code:

$posts = get_posts(array(
'numberposts' => -1,
'post_type' => 'post',));
foreach($posts as $post)
{
$arr = get_field('array', $post->ID);
$arr2 = $arr[0]['string'];
$string = implode(", ",$arr2);
echo $string;
}