How do I get/Download my Apple Developer Certificate?

https://developer.apple.com/library/content/documentation/IDEs/Conceptual/AppDistributionGuide/MaintainingCertificates/MaintainingCertificates.html

  1. Sign in to Sign In - Apple, and click Certificates, IDs & Profiles.
  2. In the sidebar, choose OS X from the pop-up menu, and under Certificates, select All.
  3. Click the Add button (+) in the upper-right corner.
  4. Select Developer ID under Production, and click Continue.

In most cases, Xcode is the preferred method to request and install digital certificates for iOS and OS X. However, to request certificates for the Apple Push Notification service, Passbook, Mobile Device Management (MDM), and Safari extensions, you will need to request and download them from Certificates, Identifiers & Profiles in your account on the developer website.
(this is the link for the sign in page for download)
https://idmsa.apple.com/IDMSWebAuth/login?appIdKey=891bd3417a7776362562d2197f89480a8547b108fd934911bcbea0110d07f757&path=%2Faccount%2Fios%2Fcertificate%2F&rv=1

^all from the first link when i Google “How do I get/Download my Apple Developer Certificate?”