Keep posts off main page?

Sure, that’s actually done pretty easily with the following function:

function my_change_home_page_category( $query ) {

   if( $query->is_main_query() && is_home() ){
       $query->set('cat', '-251');
   }
}
add_action( 'pre_get_posts', 'my_change_home_page_category', 1 );

You would add that to your child theme’s functions.php file (just create an empty file called functions.php if you don’t have one yet).

The only part you need to edit is the number “251”. That is the ID of the category you want excluded. To find the ID of the category you want excluded, edit that category in your dashboard and you’ll find it in the URL.

Okay let’s take it step-by-step. This is what you should be seeing when editing the child theme’s functions.php file: http://cl.ly/image/2y3r1H0r1t1x

If there isn’t a functions.php file yet, you just need to create a file called functions.php and put it into the child theme folder.

One word of caution, you will never break your site adding CSS, but with PHP a mistake can cause an error that will stop your site from loading. If you’re editing the PHP on your live site rather than on a local install, just be sure to have access to your serve at hand. This way, if you make a mistake in the functions.php file, you can access the file via FTP and remove the mistake. No harm done this way except the site not loading for the minute until you remove the error.