If you are using MailChimp for WP plugin on your blog already and connected it previously, you can skip this step.
Please head over to
MailChimp for WP > MailChimp area on your WordPress dashboard and click
Get your API key here. You will be redirected to MailChimp site, where you need to register/log in.
If you have been redirected to MailChimp homepage instead of
API keys page, please click on your profile name at the top right corner of page, then on
Profile menu option. On your profile go to
Extras > API keys tab.
Create A Key button, then copy entire “API key” value. Go back to your WordPress dashboard and use the key in
API key field. Click
Save Changes button.