Docker setup & cron

Hello,

could you please show an example on how to add a task to this script?
I could not find any examples on how to use this cron.sh. It seems to be a normal bash script but then how do you add a task e.g. for preview generator (occ preview:pre-generate)? I do not understand the “exec busybox crond” line already in that file, why do you need exec?
Thanks in advance!