You also need to:
1 - create a filesystem on /dev/sdb1
I don't know what you prefer, so this example creates a ext3 journaling file-system:
mke2fs -jv /dev/sdb1
/dev/sdb1 is now ready to be mounted.
2 - mount /dev/sdb1 on a mountpoint
Only you know what this new disk needs to be used for, so the following is just an example:
# create a mountpoint:
# mount /dev/sdb1:
mount /dev/sdb1 /media/ExtraSpace
/dev/sdb1 is now mounted on /media/ExtraSpace, df -h
should show this entry.
3 - automated mount during boot
If you want/need this disk to be mounted automatically when booting you need to add an entry in /etc/fstab:
# open /etc/fstab with your editor and add the following at the end:
/dev/sdb1 /media/ExtraSpace ext3 defaults 0 2
Do remember: /media/ExtraSpace
is just an example, change this to your needs.