Environment directory change

edit

I am reading the tutorials for creating a ROS environment so i can have an external one where i can edit my projects because i keep getting errors such as : fatal: could not create work tree dir 'ardrone_tutorials'.: Permission denied after command kadir@kadir:/opt/ros/hydro$ git clone https://github.com/mikehamer/ardrone_...

I have been trying to work-it out but i failed to do so. Must i create a file for my document or is there a better way of doing it? And if i need a new file how can i source it so ROS can run it?

I don’t understand the instructions of http://wiki.ros.org/ROS/Tutorials/Ins...

P.S. Beginner.