How to Make a Widget for Every WordPress MU Blog Created

1. Visit the homepage of the plug-in widget that you want to make available to all blogs on your network. Download the latest version, and if it is a zipped file, extract it. On a Mac you can use free programs that can extract archived files, and on Windows you simply have to right-click and select “Extract All.”
2. Log in to your FTP account. Navigate to the folder containing the parent site of your WordPress network. Browse to “yoursite.com/wp-content/mu-plugins.” If “Mu-plugins” does not exist, go to “wp-content” then create the folder, usually by right-clicking and selecting “New Folder.” When you are done, go into the “Mu-plug-ins” folder.

3. Upload into this folder the plug-in that you extracted. The widget will now be available on all blogs in the network. It will also be automatically active on all blogs that are added to the network in the future.