how can I change the MacBook name and password using my iCloud

You can't change your Mac's name in iCloud, as TheLittles pointed out.

You'll need to do that on the Mac itself: Change your computer’s name or local hostname on Mac - Apple Support

Hope this helps.

UniCorn007 Said:

"how can I change the MacBook name and password using my iCloud: I bought a used MacBook, and I want to change its old name & the device name using my iCloud account"

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Changing a Device Name and Password in iCloud:

You Can't. This not an option --and obviously for safety reasons. If someone got in to your Apple Account, then they could change ether password on their own will. This can only be perform on the device itself.