Henning Karlsen writes:
The library supports FAT16 formatted SD cards up to 2GB in size. 4GB FAT16 formatted SD cards might work, but is untested. Long filenames are not supported. Keep you filenames compliant with the old 8.3 standard.tinyFAT Arduino Library - [Link]
The SD card should be connected to the SPI-pins on your Arduino. Pin connections are available in the documentation in the download.