You can find very detailed instructions here. Alternatively, try these solutions:
solution. Install a program called ntfs-config, either from Ubuntu software centre, or by typing
sudo apt-get install ntfs-config
Run that program, select the disk to mount.
solution, using command line:
First, find out what the ID of your NTFS disk is. Run this program from command line:
That will a line for each partition, showing the volume UUID as well as the format. One of these should have the format "ntfs". This is your Windows partition. Now run
udisks --mount /dev/disk/by-uuid/XXXXX
where XXXXX is the UID of your Windows partition.
solution, mounting automatically at boot time: read this answer.
Please, however, note that you cannot mount hibernated Windows partitions.
Do not hesitate to come back if you have problems with any of these.