[Network Shared Media] Cannot add media

I’ve installed and activate NSM on two blog.
If I click on “add media” in post, I see NSM tab.
If I go in Media Library->Upload file, no file is then listes in NSM tab…

why?
How can I upload a file in a media library and show it on media library of another site?

tnx

http://wordpress.org/extend/plugins/network-shared-media/