SimConnect

SimConnect is a special interface that is built into FSX/P3D, and is installed automatically when you install the flight simulator.  Add-ons use it to exchange information with the simulator.  However, in some situations, P3D may not install the version of SimConnect that is required by FS Force.  If this is the case, the FS Force installer will install it for you. 

However, if you're still getting the error message that SimConnect is not installed, you can try installing it yourself.  The lib folder, underneath the FS Force folder, contains a file called SimConnect.msi.  Double-click this file to launch the installer, and then follow the prompts.