NOTE: There is another thread that gives some basic instructions but leave out some important details, especially for folks who have no idea what they are doing.
Here are some instructions for setting up your cron job on Webfaction.
Open Terminal
You need to ssh into your account. like this ssh USERACCOUNT@SERVER.webfaction.com
Enter your Password for your account
Type the following crontab -e
Press ‘i’ to go into vim’s insert mode
Insert your cron job */5 * * * * /usr/local/bin/php /home/USERACCOUNT/webapps/PATHTO/sendy/scheduled.php > /dev/null 2>&1
press esc to exit vim's insert mode
Type ZZ ( must be capital letters )
You should now see a message that says “crontab: installing new crontab”
Now wait 5 minutes and test your Sendy "Schedule a campaign" feature. If you do not see the warning box alerting you to set up a cron job then everything has worked!
Gary