If you have not edited the template code - just update the template by uploading the newest package (please remember to backup the css/override.css file if you are using it).
If you have modified the template - you have to check the changelog for the last template updates under our template updates section:
https://www.gavick.com/updates?task=group&id=4 create a full list of modified files and the merge your modified files with updated modified versions manually.