Getting started with FlyInside should be quick and easy. You'll be flying in no time!
First, make sure that your virtual reality headset is connected to your computer and working. Be sure that your monitor and headset are connected to the same graphics card, that SLI is disabled, and that your computer is setup as described in Hardware Setup
To run FlyInside just start "FlyInside FSX" or "FlyInside P3D" from your Start Menu. FlyInside ?may ask you to pick some basic settings and make some changes. Just follow the instructions one by one. You may need to restart FlyInside after these changes are made.
Eventually your flight simulator should open your monitor, while FlyInside will appear inside your headset.