Tips on Customizing Ninja Forms Contact Form – The Drag and Drop Form Builder for WordPress

How to Hide Ninja Forms Admin Menus

function plt_hide_ninja_forms_menus() {
	//Hide "Ninja Forms".
	remove_menu_page('ninja-forms');
	//Hide "Ninja Forms → Dashboard".
	remove_submenu_page('ninja-forms', 'ninja-forms');
	//Hide "Ninja Forms → Add New".
	remove_submenu_page('ninja-forms', 'admin.php?page=ninja-forms#new-form');
	//Hide "Ninja Forms → Submissions".
	remove_submenu_page('ninja-forms', 'edit.php?post_type=nf_sub');
	//Hide "Ninja Forms → Import / Export".
	remove_submenu_page('ninja-forms', 'nf-import-export');
	//Hide "Ninja Forms → Settings".
	remove_submenu_page('ninja-forms', 'nf-settings');
	//Hide "Ninja Forms → Get Help".
	remove_submenu_page('ninja-forms', 'nf-system-status');
	//Hide "Ninja Forms → Add-Ons".
	remove_submenu_page('ninja-forms', 'ninja-forms#apps');
}

add_action('admin_menu', 'plt_hide_ninja_forms_menus', 14);

Where do I put this code?

How to Hide Ninja Forms Meta Boxes

function plt_hide_ninja_forms_metaboxes() {
	$screen = get_current_screen();
	if ( !$screen ) {
		return;
	}

	//Hide the "Add-On Licenses" meta box.
	remove_meta_box('nf_settings_licenses', $screen->id, 'advanced');
	//Hide the "Append a Ninja Form" meta box.
	remove_meta_box('nf_admin_metaboxes_appendaform', $screen->id, 'side');
	//Hide the "User Submitted Values" meta box.
	remove_meta_box('nf_sub_fields', $screen->id, 'normal');
	//Hide the "Submission Info" meta box.
	remove_meta_box('nf_sub_info', $screen->id, 'side');
}

add_action('add_meta_boxes', 'plt_hide_ninja_forms_metaboxes', 20);