For adding application launchers, see this more generic question:
I think, you are asking to add a launcher pointing to a location which will be opened with nautilus upon click.
To do so, Follow this:
First create a file naming
custom in your desktop.
Open the file with a text editor (such as gedit or leafpad etc) by double clicking it
Copy the below lines and paste them in the file
/mnt in the line
Exec=nautilus /mnt with a desired location.
You can also change the string in
Name=Custom location line.
Save it by pressing Ctrl + S
Then again rename the file, pressing selecting it and pressing F2. Add a
.desktop at the end of the file.
Copy the file to your desired location. Note, if you delete the file later, the launcher will not work. I assume you copied it in
Then select the file and drag and drop it in the Unity launcher.
That's it. A new launcher will be created which will open the desired location when clicked.