Should explain very little about crontabs
A crontab is in the form of m h dom mon dow command, which translates to
minute
hour
day of month
month
day of week
Remember to use full paths instead of ones in your $PATH, as they may not be available, find which using which echo.
crontab -e
*/5 * * * * /bin/bash /root/backup.sh
Get current tty by using tty, (/dev/pts/0), then do the following.
crontab -e
*/5 * * * * /bin/bash /root/backup.sh > /dev/pts/0