The answer is different for each Astro Gold app on the different devices.

In your Astro Gold macOS the way to update depends on whether or not you have Auto Updates selected under Settings. If you do then your Astro Gold macOS version automatically updates when you are connected to the internet. If you don’t then you need to open the app, click on the words Astro Gold next to the Apple Logo at the top of the screen, then click Check for Updates from the drop-down menu.