Before you can import your scheduled tasks you need to export the scheduled tasks. Every row in the file corresponds to a new scheduled task.
The best way to do this is to create a new scheduled task and then export it to see what data is filled in. You can then use the same format for creating new scheduled task rows in the import file.
If you have set a start date in the past your scheduled task won't start immediately, instead don't set a start date to make the scheduled task start immediately. Otherwise set a start date in the future to get your scheduled task to being on the specified date.