The block should be fairly self explanatory - you pick an existing file set, select an order and the display options. It will update automatically to show any new files added to a set. You may wish to view a video covering managing files in sets.
One feature of sets in concrete5 that is perhaps less easy to find is how you can order files within sets themselves.
This block allows you to display files based on a set order, addressing the situation where you have uploaded files in the wrong order.
To change the order of files in a set:
Additional files uploaded will be added to the end of a set.
When advanced permissions are turned on, file sets and individual files have a range of permissions that can be set for users and groups.
Due to the way files sets/lists are internally managed in concrete5, the 'View Files' permission does not affect the visibility of files output by this block. Instead, use the 'Search Files in File Manager' permission to control whether files are listed by the block.
The 'View Files' permission however, is still needed to actually download/view the linked files, so in most cases you will need to set both permissions.
This field is really only useful when you have selected to display only one file from a set.
Instead of it showing the filename/title, it will override this with the text you enter, e.g. 'Latest Newsletter'.