How to set the locale inside a Debian/Ubuntu Docker container?

I'm running a Ubuntu Docker container. I have a Norwegian keyboard and need to use Norwegian characters (øæå). My Terminal character encoding is set to UTF-8 and I'm connected to my container using SSH. However, I'm unable to type Norwegian characters, nor copy and paste Norwegian characters, nor use CTL+SHIFT+U+00f8. I tried: locale-gen nb_NO.UTF-8 but nothing changed. How do I set the locale and keyboard inside a Docker container?