If you generally want to learn about access permissions and how to change them, execute:
and read through the manuals. I strongly advise you however NOT to change the permissions of anything outside your /home directory, so that you as a user can access it easily. Log in as root for that kind of stuff while leaving all the restrictions as they are. That's part of why Linux is so secure, after all.
To log in as root in a terminal, as reddazz said:
And to logout and go back to the user, just enter:
Or even quicker, on an empty command line, press Ctrl and d simultaneously.
-A