LR 5 and LR 6/CC have separate catalogs. Importing into one doesn’t affect the other. You can open a LR 5 catalog in LR 6/CC and it’ll make a copy and convert that copy to LR 6/CC format, but you cannot open a LR 6 catalog in LR 5.
It sounds like you imported things in to LR 5 after installing LR 6/CC without realizing it and now you want all those new folders to also be in LR 6/CC’s catalog, right?
First of all you need to determine exactly which folders are in LR 5 but not in LR 6.
Then go to LR 5, highlight all those folders, and use File / Export as Catalog to create a new little catalog with the settings of just those folders and their photos. In the options at the bottom when you’re naming the catalog, don’t put a checkbox in any of the four items—you don’t need to export digital negatives or build previews or smart previews. Name that catalog something that makes sense for what it contains, the small subset of photos not in LR 6, yet.
Now go to LR 6 and use File / Open Catalog and point to that little catalog you made in LR 5. LR 6 will ask to convert it and let it.
Now, still in LR 6, use File / Open Catalog (or Open Recent) and select your main LR 6 catalog, the one that is missing some of the folders, and then with that main catalog open, use File / Import From Another Catalog to add the missing folders to LR 6. You may get a question about what to do if a photo is in both catalogs. If you’ve exported only the photos missing in LR 6 from LR 5 then there shouldn’t be a problem. Otherwise, you might have to decide whether to replace LR 6’s settings with LR 5’s or ignore LR 5’s settings. Depending on how important these photos are (are they work a wedding photoshoot or just personal photos) you might have to redo some of your edits if you’ve worked on the same photo in both LR 5 and LR 6.
Thanks for such a quick response. I am glad I can import only the missing folders rather than the entire catalog. I don't recognize the new loading screen for the new LR, so I suspect I've not used it since I installed it. Feeling silly, but at least it's a simple process. I really appreciate your help.