I forgot to give credit for the tutorial I used to change my template to a three-column. There are quite a few out there, but I just ran a search on "three column template" and clicked on the first one that came up, at Tips for New Bloggers. That link takes you directly to the tutorial I used, except that I used the one for the Scribe template. There is a list of all the templates that you can change; just pick the one you're using so that what you see on your template is the same as the information in the tutorial. It was really easy, once I switched to the new Blogger. I am very resistant to change of almost any kind, but now that I've switched to the new Blogger I like it much better. It's way easier to change different page elements.
So that's how I did it. I am no computer whiz; I've learned almost everything I know by trial and error, and I'm not even real sure what I've learned! LOL