Customing code within dynamic sidebar widget

I would like to customize the code of posts listed in a dynamic sidebar. I know this is likely super easy but I’m lost.

I can change parameters of the widget in the functions.php file in my theme:

register_sidebar( array(
‘name’ => __( ‘Primary Widget Area’, ‘theme’ ),
‘id’ => ‘primary-widget-area’,
‘description’ => __( ‘The primary widget area’, ‘theme’ ),
‘before_widget’ => ‘<li id=”%1$s” class=”widget-container %2$s”>’,
‘after_widget’ => ”,
‘before_title’ => ‘<h2 class=”widget-title”>’,
‘after_title’ => ‘</h2>’,
) );

But I’m unsure on how to add the class ‘post’ to the individual
<li>‘s within that widget.
[mod: please use the code button or backticks to mark code]

Thanks in advance!