Since The7 v.5, updates for bundled plugins (Visual Composer, Revolutions Slider, Ultimate Addons, Go Pricing table, etc.) are delivered regardless of theme version.
Please make sure your theme is registered. Then navigate to Dashboard -> The7 -> Plugins, you will get “Need updating” status if there is any update available, hover on them and click update (fig. 1).
If you have quite older version of Visual composer plugin, there may be some issue updating plugin as it is re branded recently to WP bakery page builder. In such case just delete the old plugin and re install new one.