To setup your GetResponse account as an affiliate, you will need to go to the Affiliate Details page for a product that you are approved to promote and the seller has enabled the feature to share information with their affiliates.
To integrate with GetResponse, go to the Affiliate > Approved Products and click on the 3 dots beside the product you want to add your autoresponder list and select Integrations.
You will then be taken to the Integrations tab on the Affiliate Details page for that product as shown here.
Click the arrow next to GetResponse to expand that section. Here you will enter your GetResponse API Key, which can be found by clicking the link below that field, select the campaign you want to add it to or click the link to create a new campaign. Once you are done, click the orange "Save" button.