Can't sign into App store, problems with Apple ID
I installed Yosemite. Before I could do that Apple made me create a new Apple ID. Now some things won't recognize my new id and password. If I log out it shows my old Apple ID and I can't change it to put in the correct one. Also if I enter the old password that went with the old ID which it displays, it won't recognize that either. I can still get in though because I have automatic log in set.
Furthermore, I want to download the 5 updates it says I need, but the App Store won't recognize my new ID and password. As with the Log In box, it displays my old id and won't let me type in the new one. So I can't get into the App Store. Why is this and how do I get around it? Why are parts of the system still trying to use my old id but won't even let me use it because it won't recognize the password?
iMac, OS X Yosemite (10.10)