You neeed a software to decompress your FLAC files to .wav. A very common and easy-to-use software is Flac Frontend, you can download it here
With Flac Frontend you can very easily decompress your FLAC files to WAV or encode your wav audio to FLAC. You find a very good guide on this website
Alternatively, you can decompress your FLAC files with Winamp (if you have a .flac plug-in).
Just go to Options > Preferences > Plug-ins > Output and select waveOutput v.2.2.10 (out_ds.dll). Then just drag the files that you want to convert to Winamp's playlist, select the path that you want them to be saved to and click "Play".
Once you have decompressed your FLAC files to WAV, you can burn a usual Audio CD