OK, let me try again. I, too, am of an age, but no silver, just shiny, so I can jump ahead.
You download Gimp installer from here:
https://www.gimp.org/downloads/
What you end up with in download should be a file with the name, "gimp-2.10.8-x86_64-2.dmg." That is the disk image that holds the installer. The .dmg stands for Disk Image.
Now, click on that file, maybe twice, to mount the disk image. On your desktop you should see this:
That is the mounted dmg file. Also a window should open to this:
The file you can see in the window is the application, in the mounted disk image. That is what to drag to your Applications folder. Once you do that, you should see this in the Applications folder in list view:
or this
in Icon view.
But if you try to double click to launch that application, Gatekeeper, a security function of macOS will jump in and show you a window saying you cannot run it because it came from an unidentified developer. I can't post a picture of that because I'm only allowed 5 images per post, so you'll just have to take my word for it.
The way to get past this block is to right click (CMD-click) on the Gimp-2.10 and the window will open to this:
Click Open to open the application in spite of the warning. You won't be asked to do that a second time because now Gatekeeper is satisfied that it warned you about the application and won't pop up again. Gimp should open to the Gimp desktop. Gimp is now installed and you can right click on the GIMP 2.10 Install icon (the first one I posted) on the desktop and select Eject and the icon will go away. After that you can look in the Downloads folder and drag the .dmg file to the Trash.
To run Gimp, you go to Applications and click on the icon in icon view or the filename in list view.