To share your files with staff in a bulk action, simply select the files you wish to share by ticking the boxes accordingly.
Once you have chosen your files, click the cog icon to the right of the screen.
Then click share. (Read more about the move option here).
This will prompt a new dialog to appear. Here, you can then type in the names of the users you would like to share the files with.
NB: This will overwrite any existing share settings you have, so make sure you include all users who need access or this will be revoked.