You can save time by setting your Preferences for different functions including:
To open the Preferences menu go to EndNote X9 > Preferences (from the menu at the top of your screen) or use the Command ⌘ and ,
Q: When I insert a citation to my Word, I receive this message: "This library is currently being used by someone else. Please try again later."
A: This is because your library is saved in your iCloud account.
You can check if your system is set to use the iCloud for the Desktop and Documents folder:
Click on the Apple icon in the upper left corner of your Mac's screen.
Select System Preferences... from the dropdown menu.
Click on iCloud in the Preferences window.
Click on Options next to iCloud Drive.
See if the box next to Desktop & Documents Folders is checked.
If that option is checked and your library is in either of those locations or a subfolder of them, that can cause this to occur.