Latest News Module will show by default latest items from your website.You can control that from the module parameters. You can choose to show latest news from a particular section or multiple sections. Also, you can show your latest items from a single category or multiple categories.
To do that you must know the section/category id. The section id can be found in the Section manager and the category id in the category manager.
In the module parameters enter the section id. For multiple section enter all the ids separated by commas.