In any Front End File Manager block the user(s) allowed access can be selected from:
Users that don’t have access simply don’t get to see the block. You can even have multiple Front End File Managers on the same page, each set up for a different user and placed next to a different gallery block. Each user will only see their own Front End File Manager link.
Multiple templates provide:
The heading shown by the file manager can be set when editing a Front End File Manager block; you can use it to prompt users to add files to a particular set. For example “Front End File Manager – add files to the ‘Franz’s Gallery’ file set”.
While Front End File Manager is very easy to configure, to add Front End File Manager securely on a multi user site, you will also need to set up File Manager permissions at Dashboard > System > Permissions > Files.
You may also want to set up Advanced Permissions (though Advanced Permissions is not a prerequisite).
https://marketplace.concretecms.com/documentation/installation/installing_concrete5/
https://marketplace.concretecms.com/documentation/how-tos/designers/using-advanced-permissions/
By default, Front End File Manager will only upload image file types. This is usually a good security feature, because the file manager can also delete files. A missing image won't break anything.
This behaviour can be overridden globally by defining the constant FEFM_FILE_TYPE in config/site.php with any of the following values:
Note that FEFM_FILE_TYPE is a global setting and governs all Front End File Manager blocks throughout a concrete5 installation.