I've had luck with the man page for me
I create the cron's with root, for any user:
crontab -e username (or root)
And simply add the syntax et al (it's vi) save and exit.
cron.weekly is root's crons:
crontab -l root
You can add applications in the respective directory if you would like, I have one in cron.hourly to restore sound levels for ALSA, it works great.