It’s very nice to meet you. Yes, the upgrade is free. You ca go to downloads menu in your Theme forest account to download the latest pack.
In the pack you’ll find the folder wpestate. Copy the contents of the folder via FTP manager (such as filezilla) to your domain. The location of the theme installed in your domain is wp-content/themes/wpestate.
We made everything to work smoothly for all clients (old and new) during updates. You may need just to go to Appearance – Themes – activate a different theme then activate WPESTATE again, after you’ve made the theme update. You won’t lose any settings in doing so and the properties will be automatically upgraded to support the latest features added.
Let me know if you need my help.