Syncing a contact with a Mailchimp List
From any profile page do the following.
Click the purple "Actions" button on the top-right of the screen.
Select "Sync Contact"
Choose "Mailchimp" from the group of options
Once we have fetched all of your various Mailchimp lists, select which ones you want to sync the contact with.
Once you have selected a list, click "Sync"
You will see a green "Mailchimp" badge appear next to the profile name when the sync was successful.