Go to System → Settings → System
Easy serve high-resolution images to devices with retina displays. After enabling please clear the AbanteCart images cache
To generate Retina Images Apache module mod_rewrite must be installed and you need to rename the root htaccess.txt file to .htaccess
mod_rewrite is something that is installed on your server by your web host. You need to ask your host (or look in their help guide) to find out if you have it.