Problem with umlaut in Texworks

\usepackage[utf8]{inputenc}
...

and then simply

ö or \"o

You used two apostrophes (\''o) and not a single " like \"o

Like the person who asked the question, I could not get the LaTeX umlaut "accent" command to work; my attempt looked just like the weird "prime over apostrophe" that the question asker experienced. I finally figured out that the problem is that I am editing using TeXworks under Windows. In TeXworks, if I type a double quote, the TeXworks editor automatically replaces a double quote with two single quotes, which causes the problem. The solution is to reset this feature in the TeXworks editor. Inside TeXworks, click on Edit, then Preferences. Change "Smart Quotes mode" from "TeX ligatures" to "None," and click "OK." Next, click "Format," "Smart Quotes, "None." Now you should be OK.