How to reconnect the App from one Mailchimp account to another?

I have your App connected to Mailchimp account and want reconnect it to another Mailchimp account. How do I disconnect it from old one?

You can disconnect it from Mailchimp' the "Authorized Applications" page section.

1. Log in to your Mailchimp account with a web browser. 
2. Click your profile name (top right side with picture) and choose Account from drop-down menu. 
3. On opened page click the Extras drop-down menu and choose API keys (yes!)
4. Find Authorized applications section In the bottom of opened page, click the [x] next to the App you need to disconnect. 

See detailed description in https://mailchimp.com/help/remove-an-application-from-your-account/#Remove_an_Application_from_Your_Authorized_Applications article.

After disconnecting from "old" account you can open the App and re-connect to "new" Mailchimp account.