If you want to switch your Emarketing solution from Swiftpage to MailChimp, you must first disable Swiftpage. To do this, run the DisableSwiftpage component to delete any Swiftpage data in the SQL tables. You can then set up a MailChimp integration.
If you were using MailChimp, then switched to Swiftpage, and now want to switch back to MailChimp, you can run the DisableSwiftpage component to delete the Swiftpage data. You might switch back and forth between Emarketing solutions for demonstration purposes. Be aware that the component deletes the original MailChimp data including the API Key and the List ID. So although you'll be able to view legacy MailChimp data including statistics and campaign information, you won't be able to work with the data because it's linked to the original MailChimp integration.