There are several ways to get overdrive and distortion with the Bass Fly Rig. You have the flexibility of using the Drive and/or Character controls in the SansAmp section, or you can add distortion with the Fuzz in the Octa section, or with the Boost section. Each method achieves different tones. Of course, you can go nuts and use all four at the same time!
Here we focus on the SansAmp and Pre/Post Boost sections.
There are plenty of sample settings in the manual to get you started. There is, however, a learning curve of understanding how the controls interact with each other within each section (as well as with the other sections) and how you can tailor them to find your own personal sweet spot.
For more info on the Bass Fly Rig, visit:
http://www.tech21nyc.com/products/sansamp/bassflyrig.html