I dont know what exactly you are trying to schedule; but the net has loads of examples...

root@NODE% crontab -l

<list crontab>

Prepare your crontab schedule on a notepad; in terms of the minutes; hours; days; months you want to execute a particular command or script.

That command or script should be created prior to creation of the crontab ;

eg The script below would execute the isplog script every 5 min every 20 hours etc etc

root@NODE% crontab -e

5,20,35,50 * * * * /usr/bin/ttx/tools/isplog