- Create a full backup of your site. All site files and the database. You should do this to be able to restore the site in case of an unsuccessful update.
- Through your WordPress dashboard update plugins to their latest version. At least the very important ones, like WooCommerce.
- Through your WordPress dashboard switch your site to a neutral theme, like Twenty Seventeen.
- If you made customization in the theme you want to update, make sure that customization is going to be moved to the new updated version of the theme. Otherwise, you may lose it. If the customization was significant you may want to use the help of an experienced developer to properly move it to the updated theme version.
- Download the latest theme version from Envato. Prepare it for the upload.
- Delete the old theme in your WordPress dashboard or via FTP/SSH.
- Upload the new updated version of the theme via WordPress dashboard or FTP/SSH.
- Activate it (or child theme, if you use one) in your WordPress dashboard.
- Finish moving customization if any.
Your WordPress install and plugins should also be updated along with the theme. In this context you may be interested in reviewing the following materials: