The settings below can be given or taken away from each User Profile. Keep in mind, Users with the same Profile will be universally affected by changes to the Profile settings. Before changing a User Profile, check to see which of your Users are using that Profile.
The following settings affect Report and Dashboard Folder Sharing and Visibility:
To access these settings, you must be the System Administrator User.
Go to Setup, in the Quick Find search Profiles
Go to the Profiles menu, click Edit next to the Profile you'd like to change.
Hint: Use Ctrl+F to search the Profile for all settings with the word "Report" or the word "Dashboard." Using this shortcut, Windows will highlight all references to those key search words, making it easier to find the setting you want to change. Using Ctrl+F Windows search should look like this:
Watch this video when deciding who should have access to Reports and Dashboards, and some best practices around using Profile settings or Permission Sets.
See also: Report Folder Sharing Options