After opening the MACS program, you will see this loading screen.  MACS has the capability to store multiple user accounts.  This allows different users to save their personal settings, such as screen layouts and other preferences of user profiles.

To access a user profile, click on the "USER LOGIN" button (see top image).  This will bring up the window seen directly above.  If you already have a user account, a button will exist with your user name on it.  Click the button displaying your user name to enter your password.  If you don't have a user account and don't want to create one, you can click the "guest" button to log in with the default settings.

If you want to create a user account, click the "new user" button (see above).  This will display the Input box, where you type in your user name.

Once you've chosen a user name, you'll be asked to enter a password for your account.  You will also need to enter this password a second time for verification.

You can get started once you are logged in and MACS is ready.