First you need to create a directory where you will mount the partition. It's in this directory that you will see your files.
Ex: mkdir /mnt/data
To mount the partition, use the "mount" program. You need to know which devices is your partition (run fdisk -l to see all the available partitions)
Ex: # mount /dev/hdax /mnt/data
After just cd /mnt/data and do what you like