Open Poser and the library. Click the folder at the top of the library until you see a red dot on the folder called "Poser 6". Then click the little arrow and "add runtime". Browse to your runtimes and add them... don't pick the folder named "runtime" though. Pick the folder that contains that runtime folder. Whenever you want to access that runtim, click the folder at the top until you get back to that level of folders, then double click the runtime you want to access. You know which is the active runtime because it has a red dot next to it when you are at the list of your runtimes.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi