Sidebar goes to bottom sorry for rehash

Sorry to repeat what seems to be a common post/question but I also have been reading all the forum topics on side bar going to the bottom. Many are years old and the vocabulary inside WordPress doesn’t seem to match what the solvers are proposing (such as CSS??) etc.

I have Coraline theme with only the allowed customizations, no code rewriting. https://www.becvote.org

My issues with many of the suggestions for fixing: I ran through a validator and found that it shows errors, BUT I do not know where or how to fix them. I can see where they displayed the source and where they are showing me errors, but to get into the source and make a fix: HOW???

I do not know how or where to change the pixels allowed for the main text portion of a page between the two outside sidebars, if that might help.

Every page (I use pages, not posts) shows the right sidebar down low. In the Text tab when in page edit, sometimes I see no code-looking stuff at all, simply text. Is that what is meant by pasting in from Word? I may have done that, but most of my pages were built by HTML import plug in.

I did not make any changes that I recall to prompt the appearance change, and especially did not make any changes in my text widgets in the secondary widget area.