Putting something on your system path
System path is an system environment variable that contains the path for some folders where the os will search for applications, scripts, etc.
In windows django-admin.py is in C:\Python\scripts, so if you have set the PYTHONPATH environment variable and added all the required python folder in that variable like C:\Python;C:\Python\Lib;C:\Python\scripts;C:\Python\Lib\site-packages, the os will automatically find django-admin.py when you will type the command django-admin.py startproject myproj on commandline.
same with linux, the django-admin.py is in /usr/bin/django-admin.py if you install django for the default python installation.
so, one way could be if you create a alias for that script so that you can run it from where ever you want.
i am using centos and what i did is i edited the /etc/bashrc and added 
alias djangoadmin='/usr/bin/django-admin.py' and it works for me very well.
I am trying a python, django tutorial. It says type django-admin.py however I get 'command not found' with this.
Someone told me that the problem could be that django is not in your system path, what does that mean?
I am using ubuntu.