open a terminal sudo mv /Desktop/file /usr/local/share/xastir/fcc/file

you will be prompted for your password (same as your login password)

copy is cp for future reference

I would say, first check to see if you have write access to the dir you are
going to move it to, then right click on the desktop file and check
permissions to see if you can move it. In theory you should be able to open
your home folder and then move to the folder you want to copy the file to,
and drag / drop. I am not super familiar with ubuntu (just learning) but use
SUSE and do the same thing without problems.