Users are not notified or sent information when they are added to the system via SFTP Import.
If you would like to send a Welcome message to your users, you can do so via the "post a message" page or on Add/Invite Members within the group.
Users are able to choose a password by following the instructions at the passwords page of your network. To access this you will go to http://codedname.regroup.com/passwords/new, for example: http://civicplus.regroup.com/passwords/new.
Note: If you have the Single-Sign on option, they will not need a CivicReady password and can use their school login. Hence to change the password for a Single Sign on option the users will need to contact their organization's administrator.