Need more information than "they don't work". It could be they are unplugged from the wheel, the cable is bad, the pots are bad, wrong drivers, wrong settings in the drivers, you don't have them setup in LFS, wrong settings in LFS, the pedals are not inverted in LFS setup, and on...
If you have the wheel working, then you set the pedals up in LFS the same way. Press the pedals and note which axis is moving on the right. Then select that axis for the respective pedal. One thing to note is, with the Momo, you have to invert the signal. You do that right next to where you select your axis (it says "invert")
Another thing, it is possible to plug in the pedals to the back of the wheel (if already mounted on the desk/table) and miss the plug completely. It will feel like it is connected, but it isn't. Make sure it is hitting the connection.