Currently, the answer to this question is that, "You don't."
Any user in our system can only belong to one publication at a time. The publication that your account belongs to is determined by the site you used when you first submitted an event to our calendar system.
You can still post events to other sites in our network. To do so, you would simply start your submission from the particular calendar page you would like to post to. The event you post to that calendar will appear on that calendar even though your login to Meg direct you to a dashboard that is showing the logo for a different site.
If you are ever unsure of where you event was posted, please refer to this article: Where is my event?