I already answered this question to you on a private message.
1. Download original flyff ( flyff.gpotato.com ) - Search depending on which version you use.
2. Copy&Paste the folders in your resource to your client folder.
3. Use Merge, to generate the .res files and place them in your client.
4. Use your compiled neuz.exe that you've collected from your output folder after you compiled the source.
Those are basically the steps to make your own client. It's not that difficult.
An easier method would be to find a client that already fits for the server files you're using, and it's source.