How do I convert my contacts from iCloud to my Mac?
Describe which method you attempted and at which step did it fail. However, here's a working method that I used when I got my Mac.

Go to System Preferences >> iCloud and make sure you have signed in. Now the screen should look something like this:


The contacts option must be enabled and all the ones from iCloud will be automatically imported into your Mac. If this is the method you used but didn't work, please let me know.