Syncing (synchronizing) enables you to have two identical libraries (including attachments) - one on the desktop and one on EndNote Online. After you sync, all your references should appear in both Libraries.
This page explains how to sync and common troubleshooting.
Syncing for the First Time
The first time you sync a desktop library, all the references in the desktop library will be copied to the online library, and all the references in the online library will be copied to the desktop library.
If you try to use a Library that already has your references in it on my second computer, you would end up with a lot of duplicates. You can get rid of these later - see Eliminate duplicates after sync tab.
You should now have the references in both libraries.
After the initial synchronization, you can set the Sync preferences by going to Edit > Preferences > Sync.
How to Sync EndNote Desktop to EndNote Online
Sync Conflicts
If a conflict occurs, a 'Sync Conflict' group will appear in the desktop 'Groups' panel. This typically happens when you edit a reference in either the desktop or Online libraries during the synchronization, and EndNote does not know which one to keep. Select the group to open the 'Resolve Sync Conflicts' dialog and remove the conflicts.
Adapted from Michigan State University https://libguides.lib.msu.edu/endnote/syncing
Instructions and Guidelines from EndNote:
To get rid of duplicates in your EndNote Desktop Library:
1. Go to References on top menu bar
2. Select ‘Find Duplicates’
3. Follow prompts to eliminate duplicates.
Q: Can I sync more than one EndNote Library to my EndNote Online account without the Libraries merging?
A: No, you can only have one EndNote Library per EndNote Online account.
If you try to sync another Library, you will get the following message: "You are about to sync a library that is different than the last library you synced. This will merge the libraries".
Instead of having separate Libraries, consider having just one Library. Set up Groups and Sub-Groups to organize your references for different projects.
Q: Does EndNote Online support smartphones or tablets?
A: No, EndNote Online does not support smartphones and most tablets, but they do support iPads.