You need to get it from your browser. Go to the web services url and then:
Firefox: https://www.thesslstore.com/knowledgebase/code-signing-collecting-export/download-export-firefox/
chrome: https://www.comodo.com/support/products/authentication_certs/setup/mac_chrome.php
ie: https://www.sslsupportdesk.com/how-to-export-a-certificate-from-internet-explorer/