Resetting macbook pro login pswd using recovery key

I am trying to change my login pswd on a macbook pro. I have the recovery key. After entering the recovery key it warns me that 'changing the pswd will unlink my pswd from my icloud acct'. I proceed to reset pswd panel, enter new pswd but clicking 'reset pswd' button does nothing....no response. If I try to enter my login pswd again a message appears 'please enter your iCloud password as of 10/4/15' which is probably the date I last used the computer. I don't keep track of old iCloud passwords and am not sure why it is asking me this. I thought the recovery key would be enough to reset my password.