How to achieve the letters ÆØÅ on your Android keyboard?

The keyboard is not run by BxMobile itself. It is a separate app with its own choice of multiple languages. You can either change your keyboard language, or change the app.

This is an Android setting. There might be slight differences depending on the Android version, but there are mainly two places to find the settings for this.
For standard Android keyboards, the following applies
  1.  Settings --> Languages & input. Here you can choose language for the specific handheld unit. On some units you also have an option for "Keyboard & input methods". Below "virtual keyboard" you can set up which keyboard to use, and from there choose a language. This is the setup control for the letters ÆØÅ, and also whether to use comma or punctuation as a decimal sign. 
  2. You can also find the keyboard settings by pressing down on the space button on your on-screen keyboard. From here you can choose which keyboard you wish to activate. Notice how most keyboards has their own in-app settings button.

In some cases you might have to download the Norwegian keyboard, and in most cases you will just be asked for permission to download, and it will work from there. But on some units, it might be a bit tricky.