The magazine files themselves cannot be transferred to an SD card. The magazines are in a secure format and will live in the same folders as the application itself. Depending on your device, you may be able to move the "application" over to the SD Card and still have it operate normally, but most devices do not support this feature.
Here are the steps you can try:
- Go to 'Settings'> Device
- Select 'Applications'
- Select 'Manage Applications'
- Locate and select 'Zinio'
- Select 'Move to SD card'
Please note that magazines cannot be stored on an external SD card by themselves and that your issues must stored within the application. If you need to make space on your device, simply archive some issues from your device, you can always restore them at a later time.