you can keep a backup of the current version you are using in your website before doing any update.
To get auto update features you can use Envato Market WordPress Plugin. This plugin helps customers receive updates to their premium wordpress Themes & Plugins purchased through Envato Market (ThemeForest & CodeCanyon).
you can download the plugin from here:
Using this Envato Market WordPress Plugin you will see:
- Latest version (need to update version) number
- Details view option for the latest version
otherwise you can download the update version from Envato Market Downloads page then you can over write the plugin by replacing with the latest version using ftp. After uploading the latest version try to active the license using the latest purchased purchase code.