If you want manually update WPBakery Page Builder login to support.wpbakery.com and download the latest plugin version. Then install it the same way as you did the first time (WP Dashboard -> Plugins -> Add new).
Automatic updates are available with an active support tenure. If you want to set automatic update – first go to WP Dashboard -> WPBakery Page Builder -> Product License. And click Activate button. Step by step instructions.