You need to create an EndNote Online account before you can use EndNote on an iPad. You can then download the EndNote app for iPad to view and edit your EndNote library on your device.
To download the EndNote app go to the Apple App Store and search for and download the free EndNote app.
When you open the app for the first time you will be asked to log in or create a new account. You can use your EndNote Online account details to sign in (if you do not have an EndNote Online account or other EndNote libraries you can create a new account at this stage, but it will create an empty library.
Once you have signed in your EndNote Online libraries will be synced to your iPad.
You can add, edit, and search your EndNote references using EndNote for iPad. You will not be able to use the EndNote for iPad app to add references to word documents.
Clarivate has produced a very helpful video on using EndNote for iPad: