Supposing you did copy the correct keys, you need to add your identities to ssh-agent. Try the following:
ssh-add /Users/<username>/.ssh/id_rsa
Where <username>
is your username and id_rsa
is a private key. It's important to use the absolute path. Upon success, you'll see something like:
Identity added: /Users/johndoe/.ssh/id_rsa (/Users/johndoe/.ssh/id_rsa)
Repeat for every key you want.