OPTION 1 - AUTOMATIC UPDATE:
Download and Install the official Envato Market WordPress plugin here
Follow the instruction on the Envato Market WordPress plugin official page.
When the theme update is done, please go to WP-Admin > Appearance > Install Plugin and click "update" for every plugin that requires an update.
If for some reason you see some code on your front-end website after the theme update, make sure that all the required plugin are activated by going to WP-Admin > Plugins.