Lisa,
Select all the target images in the Develop module filmstrip. Make adjustments to the 'most selected'
There should be a button at bottom of Develop Right Hand Panel, called 'Sync ...' Click that, and you should get a dialog asking which specific settings are to be sync'd/copied to the other selected images.
Alternatively, select all the target images in the Develop module filmstrip. Hold down cmd/ctrl, and the 'Sync....' button turns to 'AutoSync', click that, and any changes made to the 'most selected' will be sync'd to the remaining selected. Don't forget to turn it off when you're done, that causes no end of headaches.
If you will be applying exactly the same settings to multiple shoots, you can save a develop preset with those settings. There are several aways to apply develop presets to numerous images.
I'm not sure why your sync button is grayed out in Library.