thank you for responding.
In order to analyze the problem I will give a brief description of what my goal is, what I have done so far and what problems I encountered:
Goal: to have a place (directory) where I can store files (pictures) that can be used in different courses, even across categories. After doing some reading in the moodle docs I thought that a file system repository (http://docs.moodle.org/22/en/admin/repository/filesystem) would do the job.
What I have done so far:
I have followed the instructions given in http://docs.moodle.org/22/en/admin/repository/filesystem.
But already in the first step ("Creating folders for your file system repositories") I encountered a problem as it says "Find the moodledata folder on the server" : and there was no such folder.
Doing some more reading I found http://docs.moodle.org/22/en/Moodledata_directory where it says "The moodledata directory is initially created with an initial install of a Moodle site. Site administrators can see the actual moodledata directory name and location in the config.php file."
In config.php I find "$CFG->dataroot = '/home/www/moodledata';", but again I do not find this directory structure on the server.
To be able to continue I created these directories myself: /home/www/moodledata/repository/pics.
The next problem occured in the step "Setting up a site-wide file system repository": after clicking on "create a repository instance" I expected that I would be able to select the folder pics, but there was no dropdown menu (and typing "pics" didn't work either):
The message "You need to create at least one folder inside the /home/www/moodledata/repository/ directory so you can select it here.", despite the fact that there a folder pics. After removing the directories I created earlier (/home/www/moodledata/repository/pics) the same message appears, what could indicate that moodle does not recognize this folder structure.
That's how far I got ...