When you have the system set to automatically mount drives when opened, as you do, then when you access it with the file manager, it gets mounted at /media/name, where name is either the label or number. You can see the path in Nautilus by pressing Ctrl-L, which will expose the full path in the Location bar above the file listing (you can type in this bar, which is handy).
If you want a partition to be available all the time, you can manually mount it or have it mounted automatically by making an entry in a configuration file /etc/fstab. It seems complicated at first, but after you've done it a few times, it starts becoming easy. Being NTFS makes it slightly harder due to the way permissions are handled, but the way I do it is thusly:
In a terminal, enter the following command (informational, makes no changes):
sudo blkid -c /dev/null
This will list all the partitions, along with the labels, UUIDs, and type. This is all the information you need to mount the partition.
You will need to find the partition(s) you wish to mount from the list. The windows partition will be listed with TYPE="ntfs".
To make it automatically mount on startup, you will want to first decide on where to mount it. This depends on whether your system is only used by you, or shared. If it's only used by you, the easiest way is to create an empty folder in your home directory, using whatever name you want, such as "windows". Then, edit the file /etc/fstab, using sudo. If you use gedit, enter
sudo gedit /etc/fstab in the terminal.
Skip to the bottom and add a single line like this (assuming your username =
username, and the UUID is
012345678987654321 for the example):
UUID=012345678987654321 /home/username/windows ntfs auto,users,uid=username,gid=username,utf8,dmask=002,fmask=113 0 0
To test it out, you can manually enter a command to mount everything in fstab:
sudo mount -a
What this does is try to mount all lines listed in fstab; if there is a problem, it will tell you right away, and you can either figure it out on your own, or ask back here.
If it works, you will see your windows partition in your home directory.
If you want to mount it in the /media folder, you'll need to do a bit more work, as you will need to set the permissions for the folder which belongs normally to root.