Here's a basic Step by Step:
Press “m” to get the help menu
Press “p” to print existing partition table
Press “n” to create new partition
Press “w” to save the partition created
To re-probe the partitions that you created. If you don’t run this command, the kernel won’t be able to see the partition.
This command is to format the partition with ext3 file system.
# mkfs.ext3 /dev/sdaX
Mount the partition into a mount point to begin using it. You have to make that directory first of course.
# mount /dev/sdaX /mnt/data
Finally, you might want to make it permanent by adding the line in fstab.
# vi /etc/fstab
/dev/sdaX /mnt/data ext3 defaults 0 0