Issue
I have downloaded several applications for my Nokia N9, but my phone won't let me install them. What can be done to handle this issue?
Solution
By default the Nokia N9 allows only the installation of software downloaded from the Nokia Store. To be able to install and use third party applications on your
phone, you must first enable a certain option. Here's the procedure:
From the Home screen > Tap on Settings > Applications.
Once in the "Manage applications" menu, select "Installations".
Check "Allow installations from non-Store sources"