do
man crontab
man tar
man vi
read some docs firs, and you'll get everything explained from basics
...
I'm not sure what exactly are you trying to but you need to edit crontab similar to this
crontab -e Username
5,0 * * * * /home/tarscript > /dev/null 2>&1
and then edit tarscript like this
tar cvfz /home/yourtaredfiles.tar.gz /home/yourdir/
|