config cli password rwa <username> (after entering this you will be prompted for passwords).
For example, to set the Login and Read/Write password to:
Login: esean2k
Password: password2k
config cli password rwa esean2k
Prompt will then ask you for the old password.
The next prompt will ask you for the new password, put in: password2k
The next prompt asks you to confirm that password
At that point you're done...no need to save anything. Repeat for rw, ro, etc..if you want to change those too.