Hi
Place the SD card in the memory reader.
Open a terminal session and run the following command as root
fdisk -l
This will list all the disks attached
You should look for the something simular to the following
Device Boot Start End Blocks Id System
/dev/sdc1 * 1 3819 977648 b W95 FAT32
To mount the SD you can do the following
mkdir /media/sd
mount /dev/sdc1 /media/sd