- open konsole this brings up a shell prompt.
type
into that shell prompt, this brings up the manual pages for tar and will go through all of its commands.
Now that you've done that, read through the commands list, and fully understood them create a new directory called openarena
move the tar.gz file into that directory.
mv oa*tar.gz /path/to/your/openarena/
move into that directory
cd /path/to/your/openarena/
Use your new found knowledge of tar gleaned from the man pages to extract the file into its own directory. Easy.