First, login to your Mail Chimp Account account.
For your API Key, click on your name at the top right, click Account. Now, click Extras > API Keys, then click the Create A Key button and name your API Key as your want. Check this screenshot below for more details.
For your List ID, click on Lists in the menu, if you have no list created, create one and click Settings > List name and defaults. From here, you will see your List ID in red. Check this screenshot below for more details.
Then, you just need to navigate to your Splash Access Dashboard, General > Mailing/List > > MailChimp and enter your IP Key
Navigate to the Access Point Location Tab in Splash Access
Load all teh Access Point Mac address from the Import Aps button if you have set up the Meraki API or Enetr trhe device mac manualy and the the List ID per access poiunt