do you try to access via EndNote from your Uni or from home?
Normaly you can add Login-Data to the connection file via “Edit -> Connection Files -> Open Connection Manager -> look for the one you want to Edit -> Edit ->Connection Settings”. There you can add UserID and password. Save it under a different name (add “Copy” e.g.).
Or you could ask your library at your Uni, they should know what to do, if it doesn’t work.