You do not need a password for SyncNow, or a copy of the site on your PC.
Sign up asks only for your first name, last name and email, and confirms the email with a 6-digit code. For the site you need the FTP server, port, user and password, and you choose the folder that holds the site on the server; SyncNow tests the connection before it creates the project. MySQL databases are optional and can be added later in the project's Connections tab.
Agents work through the SyncNow app on that PC, so it has to be open and signed in while they work. Start by installing the app: see How do I install the SyncNow app on Windows?.