iMac updated Apple ID in ElCapitan. iCloud does not allow log in.

Got a new email address and so my Apple ID updated. On start-up iCloud now informs me that I must sign in, and when I do, tells me my info is incorrect. What I am realizing (ill-informed as I am) is that this 'connection' with iCloud was discontinued some time ago. My iMac is early 2009 and running El Cap. So . . . thanks but there is no fix other than a new computer.