Get a nice low bass tone. Open it as a sample. Now set loops points on the wav. This can be done with the "crf" knob. Engage the knob and set the points over a nice area, as this'll be the area that creates the overall bass tone.
Now on playing the note, you'll hear that its a continuos monotone. Key notes can be easily manipulated in the fruity keyboard. *important* to shut a note off, simply play the note again, but silence it, ie. velocity = 0.
To add some nice wubb! to the bass line, select INS on channel sttings, and mess with the fast LP filter. Set cut to (estimate) 10 o'clock and res to 3 o'clock. Then select the CUT option for the LFO. Set the amt and speed to the desired wubbing noise. ie amt = how much wub, speed = how many wubs.
And there you go, it takes a little practice to control these knobs, but its fun and easy once you give it a go and find your feel. the cool thing is you can also do a wubbing solo and record it, and fruity will memorise that knob, and you can go back and do some more shit. Its crazy isn't it? But its cool and you know it.