hey man,
If im right you have to check your midi settings to see if flstudio is recgonizing your controller input and click the enable light.
after that right click on any button in flstudio and click on link to controller.
from here there is 2 ways to do it...
you can highlight auto detect and once you turn a knob it will know what midi paramter to set to that knob. in that case you have to make sure there is some midi tamplete set on your controller so that flstudio know what cc number to detect otherwise if your dont have anything set on your controller then your knobs are not turned on and will not auto detect.
the other way to do this is turn off auto detect then set a channel and cc parmeter, for example (Channel 1 and CC 1) in the link to controller specification box of flstudio. now the knob or whatever, you just set knows to read from midi channel 1 and CC 1 right? anyways now you have to go physicly go to your midi controller and decide what knob or whatever you want to controll. once you have decided then look in your manual on how to set the Channel Value and Constant Control value (in this case you want to set it to Channel 1 and CC 1 right?). and presto once of save your values on the controller you knob will now move in sync with flstudio.
other then that what i mentioned at the very top is VERY important... if your midi controller is not in the list then you will have to install the firmware off the cd if you havent already.
another thing i had trouble with was that even though i did all of this it still didn't work. EVEN though i did it all right, what was happening was my controller (BCR2000) need to be set up in the GLOBAL settings of the midi controller itself. mine had 8 settings, 4 of which being for usb midi controlling and the other 4 being for direct midi cable midi controlling. All at the end of the day if you have the same problem then first make sure you have a knob programmed and try different global settings like i mentioned.
P.S. I noticed with flstudio that when a global setting is changed on the controller then they will stop comunicating together. so once you change a global setting on your controller you must go to the midi settings in flstudio and turn off the enable button and turn it back on right after.
other then that good luck haha
have fun spending the next week programming your controller.