The MainWP File Uploader Extension allows you to upload files to your child sites from one centralized location. It gives you ability to upload multiple files to all of your child sites at the same time. To do that go to: MainWP > Extensions > MainWP File Uploader Extension tab and click Choose File button:
When you locate the file on your computer enter a path where you want to upload your file(s):
In the first part of the path you have 4 options to choose. In the select box you can select one of the 3 default WordPress directories (wp-admin, wp-content and wp-includes) or to select the child site root directory ( / ).
After that select your child sites where you want to upload your file(s) and click the Upload File button.
