As stated in our policy with your purchase of a theme you are eligible to receive free updates for life. You can keep track of the latest version of all our themes in our wiki pages http://wiki.morethanthemes.com/.
In addition, every new theme release is accompanied by a wiki page with update instructions.
With that said, just send us email with the product name and your order id and we will email you the download link for the latest theme release.
More Than (just) themes