Extracting Files and / or Copy files

[Jan Sneep]

I'm trying to extract a file from a tar.gz file which I downloaded onto my
desktop.

I used a terminal window, Applications -> Accessories -> Terminal, to create
the /opt/open-xchange/lib folder using mkdir. That worked fine, I downloaded
the tar.gz file from the website successfully to my desktop and when I
double-click on the file in the Desktop - File Browser the archive opens and
I can extract the file I need to my desktop, but it won't extract to the
/opt/open-xchange/lib folder because I don't have permission.

I have looked in the help to find out how to change the permissions for that
folder, but going though the File Browser and selecting the Properties and
then the Permissions tab, it shows "root" as the owner, so I can't change
the permissions. Then I thought I would try and copy the file from my
desktop to the lib folder in the terminal window, but "copy" isn't a
recognised command.

So how do I either ... login as "root" ... or give Extract sudo permissions
... or what is the equivalent to the old DOS copy command???

Help ! and Thanks,

Jan