You will need "Page Ownership" or "Webmaster"  permission to add page elements. 
  1. Sign in and turn on Edit Mode
  2. Go to the page that you want to add your MailChimp element to. 
  3. Click Add Page Element
  4. Scroll about halfway down, choose the MailChimp List Subscription Form element. 
  5. Input your Form Title
  6. Copy your API Key from your MailChimp account
  7. Click Fetch Lists, choose your "Mailing List". 
  8. Click Create This Page Element