At the top of the headlines page, there is an area for you to have a welcome messages for new members. Currently, it's been hard to return to this message to make edits after you've created one.
You can directly visit the message to edit it by appending the following after the '.com' of your address (and removing any /forum or /headlines that might appear in your address bar):
/wizard/welcome_members/
For example, on the support forum, I would type in:
http://support.lefora.com/wizard/welcome_members/
In the future, we'll provide more options to edit your welcome message and email welcome messages from your admin panel.