I'm no expert. I think FL has a user forum that might be a better resource so you may want to check there too.
If you have the FL soundfont player or a third-party player (such as sfz), you can assign midi to that channel and import full drumset soundfonts. I don't if FL has full drumsets that are soundfonts, but there are several that can be downloaded for free, such as at the Hammersound Web site.
Another option is to split up the drum channel by individual drum parts (snare, kick, hi-hat, etc.). Some midi files have been programmed this way and others have the drums all in one channel together. In the latter case, you can copy the channel several times and then edit each one to remove everything but one part. For example, take out everything but the snare drum and assign a snare drum sample to that channel. In the next track, take out everything except the kick drum and assign a kick drum sample, etc.
Hope that makes sense. There's probably other options that work just as well. Good luck.
ONE OTHER SUGGESTION: Depending on the recording software you use, you can also import midi files and soundfonts without using Fruity Loops
at all. I have n-Track studio and it does this very easily. You can assign a soundfont to each midi track, render it to a wav file and then go back do another midi track, etc. There are some high quality, free soundfonts out there for drums, bass, keyboards, etc.