Send the following code via Unix command in ARD to log in. Be sure to change ‘usernamegoeshere’ and “passwordgoeshere” to their correct values for your systems. Lastly, this code snippet assumes the username field is currently selected on the remote system.

osascript -e
'tell application "System Events" to keystroke "usernamegoeshere"';
osascript -e
'tell application "System Events" to keystroke tab';
osascript -e
'tell application "System Events" to keystroke "passwordgoeshere"';
osascript -e
'tell application "System Events" to keystroke return'