Scheduled tasks aren't the easiest thing to understand from the documentation which can make them tricky to get working right. The key thing to remember is that a ScheduledTask is nothing more than some block of code to be run periodically with the result essentially discarded (though it will be written into the task log but not in a way that is easily accessible for computation). To start, you should write code in an interactive session that does exactly what you want. In this case, it is something like import data from an external source, modify it, and finally save that result somewhere. Remember, the result of a scheduled task isn't saved anywhere for you; you have to decide where you want it and CloudPut or CloudExport it. When it works interactively, you can create a ScheduledTask expression that contains that code you want to run with the frequency you want it run. The scheduled task will run exactly the code you give it so be sure it contains all the operations needed. If you want to run that in the cloud, all you need to do is CloudDeploy the expression and it should start working. Note that the highest frequency you can schedule in the cloud is hourly. Also, don't use the RunScheduleTask function which doesn't do what you think when run on cloud objects and I believe is going to be deprecated.
If this doesn't really help you, I suggest just trying to write the code in an interactive session and get the result you really want. If you have questions about just that I'd be happy to help. When you have that part working, try deploying a SheduledTask to the cloud. If you log in to the cloud you can see it listed in your Scheduled Tasks list in the Cloud Files side panel. There's a context menu you can use to run the task immediately to see if it worked the way you expected. I can also help you with this if you are still having difficulties.
And finally, to be honest I find postfix notation very challenging to read. You may want to avoid that except for trivial cases.
