If you need step by step instructions for creating a custom app from scratch, then you should be looking into the filemaker training series, or other training series like Lynda.com that will teach you how to develop in filemaker.
There is not really specific training guides for "create __X__ thing from the ground up".
The starter apps that are included in filemaker are a good place to start most of the time though. There is a contacts app that is included. You would just need to learn how to augment this with a related "messages" table.
Contacts.fmp12.zip 382.4 K