In your dashboard, head to MemberPress -> Activate -> Addons and click to install the GetResponse addon. Once it's installed, activate it and you'll see the GetResponse integration available in the "Marketing" tab of the MemberPress Options page.
Head over to GetResponse.com to login and then click on your profile to expand a menu list. Click on Account Details.
Then click on API & Oath option from the left side of the page.
Locate your API Key on the "My GetResponse API key" page.
Once you have completed the steps above, by default, MemberPress will automatically add the email address for everyone who signs up through your membership registration form to your Global email list in Aweber. MemberPress never removes a user from the Global list.
Once you have GetResponse enabled, a new option becomes available under the "Advanced" tab of the Membership edit pages. This option allows you to select a list that only members who purchase that Membership should be added to. Members will be automatically added to or removed from this list depending on their current Subscription status for this Membership. This list must be different from the Global list you have specified in the Options, and should be different from other Per-Membership lists as well.