I can't help you much as I'm a Windows user and don't use an SD card anymore, but in Windows the external SD card shows up as an extra removable drive when connected to the PC via USB and should show up also in calibre. If you've formatted the card in the T1 there should be a basic Sony directory structure created on the card
If I remember correctly the T1 sees the path to the root of the external SD card is something like /mnt/extsd/ and root of internal memory as /mnt/sdcard/
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