1) select the folder where you want to save the file.
2) set a file name (or accept the suggestion)
3) select format. For writing to a CD you should choose "WAV". Note that only MP3 files may contain Karaoke lyrics.
4) if you have selected a format that allows compression, you should now select compression mode/degree
5) if you want to mix down the final tune in an external mixer you may choose to render each MIDI channel into a separate file
6) in Options you can choose to have the loudness normalized. In this case, SynthFont2 creates an intermediate file with full 32 bit dynamic range and when finished reduces the bit depth to the desired one and normalized the output level.
7) when playing to the speakers you may choose to reduce the number of concurrent voices being played at the same time in order to avoid CPU overload (and sound gaps). When playing to a file you may still want full voice range as there will be no sound gaps due to CPU overload in the file.
8) when creating an MP3 file you have the option to store Karaoke lyrics in the file.
8) you can as well specify some Meta tags you want to store in the file.
9) Loudness level - you may manually set the loudness level to a different value than what you have for speakers only.