The procedure you describe is correct, Mike. Just install SDA, which will install the necessary shared components like SAM and eLicenser Control Center (sadly still required for some license checks for things that have not yet transitioned to Steinberg Licensing), then go to My product downloads on the left-hand side in SDA, choose Dorico Pro 4, click Install All on the right-hand side, then have a cup of coffee while you wait. Once all the progress bars turn green, run Dorico 4, sign in when prompted, and you’re done.