How do I go around setting a new iCloud Keychain in my laptop when system preferences do not let me open iCloud settings? Should I buy a new computer?

Suddenly my laptop started to ask me for the iCloud Keychain password, which it never did in the past. I thought I know it, but apparently I was wrong. After unsuccessfully asking several times, safari, pages and iCloud system preferences will not work. So now I tried to circumvent the issue following Apple‘s instructions for the iPad touch and the iPhone, which did not work because my devices have different interfaces and, apparently not the same options. Is there a way to sort this out, or do I need to trash the notebook since it became useless? Can anyone help? Thank you.