Please have a look at the information in the WordPress Codex which we already linked in the previous replies, there you’ll find everything you’ll need and you can customize the query of the particular widget as you like.
The WordPress Codex contains an example of how you can support custom post types within your query, here it is:
$args = array(
'post_type' => array( 'post', 'page', 'movie', 'book' )
);
$query = new WP_Query( $args );
Keep in mind that if you modify core theme files within the parent theme, then your changes will be lost after theme updates.
That means you might want to consider coding a custom version of the MH TechMagazine theme (which is a child theme for MH Magazine lite) under a new folder name and then apply your customizations to your custom child theme as you like.
In case you don’t know how to override PHP functions from the parent theme within a child theme, then you can find information here: How to override parent theme functions in a child theme.