How to Hide OnePage Checkout Lite for WHMCS Admin Menus

function plt_hide_onepage_checkout_lite_for_whmcs_menus() {
	//Hide "OnePage Checkout Settings".
	remove_menu_page('onepage-checkout-lite-for-whmcs');
	//Hide "OnePage Checkout Settings → Layouts".
	remove_submenu_page('onepage-checkout-lite-for-whmcs', 'onepage-checkout-lite-for-whmcs#tab=layouts');
	//Hide "OnePage Checkout Settings → WHMCS API Options".
	remove_submenu_page('onepage-checkout-lite-for-whmcs', 'onepage-checkout-lite-for-whmcs#tab=whmcs-api-options');
	//Hide "OnePage Checkout Settings → WHMCS-Sync Social Login Options".
	remove_submenu_page('onepage-checkout-lite-for-whmcs', 'onepage-checkout-lite-for-whmcs#tab=whmcs-sync-social-login-options');
	//Hide "OnePage Checkout Settings → Paypal API Options".
	remove_submenu_page('onepage-checkout-lite-for-whmcs', 'onepage-checkout-lite-for-whmcs#tab=paypal-api-options');
}

add_action('admin_menu', 'plt_hide_onepage_checkout_lite_for_whmcs_menus', 11);

Where do I put this code?