There are several ways to create a Developer ID application certificate. We'll go ahead and describe to more straightforward way to accomplish it
- Be a member of the Apple Developer Program
- Having Xcode installed on your machine
- Open Xcode
- Once it's loaded, open the "Settings" menu
- Select the "Account" tab in the window, and click on "Manage Certificates..."
- A new window will open, then you can click on the little "+"
- Select the "Developer ID Application" in the dropdown menu
- You should see a new certificate appear on the menu