Ruins has support files in /mods/resources/ruins followed by lots of biome folders and folders called /generic and /templateparser. This file structure can be found intact in instances of minecraft with modpacks containing ruins.
Okay, I found the reference, and no ruins.txt shows up in the instances of minecraft (that i'm running) that have ruins installed in a working state.
3b. Edit /mods/ruins.txt, and any template files for weight, to fine-tune your experience.
This is how I check to see if ruins is installed:
type "/testruin tester" in chat in creative mode, and one of the following will happen
= "Unknown command" - ruins is not running in minecraft
= "no permission" - go to creative mode and retype command (if it's any of the last 3, then ruins is installed and running)
= "filepath does not exist" - it was looking for the file tester.tml in mods/resources/ruins/templateparser
= blocks spawn at your location - Success!
Knowing which one of the above helps in figuring out what part of the installation is missing. Usually it's running with no structures, or something is in an unexpected place, like another /mods folder inside the /mods folder, which it is only looking for one.
At Gillymoth's suggestion I have downloaded and installed ATLauncher. I added Forge 1.8 and Optifine and created an instance with vanilla MC version 1.8.
When I click on Run it shows a small flash screen that indicates something is loading or updating and then .... nothing. It won't run.
Why won't it run?
(When I load the instance of vanilla MC, it gives me the message that I have the 32-bit version of Java loaded and I should have the 64-bit version. I just recently - a month ago - loaded the 64-bit version of Java. It also asks me if I want to download the latest version of - I presume - ATLauncher, even if I just "downloaded" it seconds before.)