The easiest way would be to use a GUI:
For Gnome use gnome-schedule (universe)
sudo apt-get install gnome-schedule
For KDE use kde-config-cron
It should be pre installed on Kubuntu
But if you use a headless linux or don´t want GUI´s you may use:
crontab -e
If you type it into Terminal you´ll get a table.
You have to insert your cronjobs now.
Format a job like this:
* * * * * YOURCOMMAND
- - - - -
| | | | |
| | | | +----- Day in Week (0 to 7) (Sunday is 0 and 7)
| | | +------- Month (1 to 12)
| | +--------- Day in Month (1 to 31)
| +----------- Hour (0 to 23)
+------------- Minute (0 to 59)
There are some shorts, too (if you don´t want the *):
@reboot --> only once at startup
@daily ---> once a day
@midnight --> once a day at midnight
@hourly --> once a hour
@weekly --> once a week
@monthly --> once a month
@annually --> once a year
@yearly --> once a year
If you want to use the shorts as cron (because they don´t work or so):
@daily --> 0 0 * * *
@midnight --> 0 0 * * *
@hourly --> 0 * * * *
@weekly --> 0 0 * * 0
@monthly --> 0 0 1 * *
@annually --> 0 0 1 1 *
@yearly --> 0 0 1 1 *