Retrieving & Updating Lists
Once your MailChimp API keys has been set up, you can start using the addon and retrieve all the lists that you've created on MailChimp. To do so, press the "Reload MailChimp Lists" button at the bottom of the MailChimp's settings page in Users -> WPUM Settings -> Extensions of your WordPress dashboard.
You can use the button to reload lists as many times as you want. This is useful if you change something within your MailChimp account. Once the lists have been updated/loaded, they will appear into the settings panel under the "lists" section.