In your WordPress template put your desired sep (separator) in the wp_title() tag. So if you want to use the pipe | character, your wp_title should look like:
wp_title('|')
This is usually in the head.php file of your theme. Most likely between the <title></title>
HTML tag.
For my themes, I use the following PHP which can be used conditionally with or without SEO by Yoast:
<title><?php
### Print the <title> tag based on what is being viewed.
global $page, $paged;
if(defined('WPSEO_URL')){ // If Using WordPress SEO Yoast - let it override
wp_title('|');
} else {
wp_title( '|', true, 'right' );
// Add the blog name.
bloginfo( 'name' );
// Add the blog description for the home/front page.
$site_description = get_bloginfo( 'description', 'display' );
if ( $site_description && ( is_home() || is_front_page() ) ) {
echo " | $site_description";
}
}
// Add a page number if necessary:
if ( $paged >= 2 || $page >= 2 ) {
echo ' | ' . sprintf( __( 'Page %s', 'Test Theme' ), max( $paged, $page ) );
}
?></title>
The above will allow you to use the %%sep%% designation in SEO by Yoast and use your own separator character.