Are you trying to compile 64-bit application? If yes, please, note that Flash'In'App is 32-bit framework and can't be compiled to 64-bit application.
If this is not the case, then please, let us know the following:
1. Can you compile successfully Flash'In'App samples?
2. Have you added Flash'In'App framework to your project (right-click project tree > Add > Existing framework)?
3. Have you added to target copying Flash'In'App into the application (right-click application target > Add > New build phase > New copy files build phase)?
If you've done all the above and still get the error, please, send us to support[at]eltima.com a sample project illustrating the issue for investigation.