First you should download CyberDuck from the official website and install it on your Mac.
Then start the application and click Open Connection. In the new window enter the following details:
Server: here you should type your domain name or the name of the server that hosts your account i (e.g. siteground200.com)
Username: here you should type your FTP username (e.g. email@example.com)
Password: here you should type your FTP password (the password for firstname.lastname@example.org)
To use Passive mode for the FTP connection, click More Options and from the Connect Mode drop-down menu choose Passive.
Click the Connect button and you will connect to your account via FTP.