Ubuntu's security policy does not allow anyone to become root (see here and here).
Instead preface every command with
sudo and then use your password to gain root privileges for that command.
Copy a file to a directory owned by root:
sudo cp ~/example.txt /etc/example.txt
cp ~/example.txt /etc/example.txt
To change the privileges of a file owned by root:
sudo chmod 775 example.file
chmod 775 example.file
You don't actually ever need to become root; you can always use sudo to preface commands that require root privileges.
For applications that have a GUI, use
To edit a text file owned by root:
gksudo gedit example.txt
If your want to browse/copy/paste/etc. files using a GUI you can run
All of these commands can be entered into a terminal, or, if you'd prefer to not use a terminal, you can just press
alt-F2 and enter the commands there.
Hope this helps!