To update Listimia theme do the following steps:
First of all make a backup of all the customized theme files, so you can recover it and redo all changes at any time.
Download the latest theme version and extract the package to your Desktop.
Using your FTP program, upload the content of the "UPLOAD" folder to your phpMyDirectory root directory (where index.php is located).
After successful upload, you should go to your admin panel Plugins -> Listimia_options and click Refresh link from left side menu.
Redo your changes by merging your customized files with the new ones.