Installing Apps Not in Nokia Store

By default, the lovely people at Nokia disabled the ability to install applications outside of the Nokia Store to protect many users from installing virus laden applications or those that Nokia are unable to verify as legitimate software. 

However we are not at Apple. There is a a built-in way to enable the installation of .deb files on your Nokia N9. It's as simple as this: 

Go to Settings application - Applications - Installations - Allow Installations from non-store sources 

You can now click on .deb files on your N9 whilst browsing the internet and download them to your phone. However if you prefer, you can download applications to your computer and transfer them to your N9.