Hey alinewbie,
The only way that I know of to create a new directory in Joomla is through the media manager in Joomla administrator control panel. Here's the steps you need to follow:
Control panel --> Media manager button --> Type in the directory name you wish to create on the create directory field --> Click create button
Voila! you have a new directory.
To reference/link the file you've just created, you can either use an absolute path or relative path:
Absolute path:
http://www.mydomain.com/images/ style="color: #0000FF">newfoldername/filename.ext
Relative path:
images/newfoldername/filename.ext
If you want to link to images you've uploaded to the media manager using Joomla's {mosimage} let me know. It's another way to link to an image without having to know the exact name of the image file you've uploaded.