To start a new conversation from the web application, go to Messages and click Compose new message.
Click in the Start writing… field to select your recipients. You can send a message to a group or to individual users, but only users that are member of the same user group(s) as yourself will be available.
Click on a user group or individuals to select your recipients. Add the subject and your message body and click Send message. Note that both subject and message body text are mandatory and that the Send message button will stay disabled when they are empty.
While composing your message it will automatically be saved as a draft. If you need to pause your work and leave the message without sending it, the draft message will be saved and you can easily find it by looking for messages marked with Draft in the inbox, or use the draft filtering option. If you want to delete your draft you can simply click Delete draft in the bottom left corner.