Hi Mikey, for a bike frame like that you'll probably want to draw several center-line curves and then create tubular surfaces around them by drawing a circle and then using sweep with 1 rail.

The tutorial that Pilou links to above would be good to review - even though that's for Rhino you should be able to follow along quite well with MoI and it should give you some good strategies on how to approach the whole project overall. Here is a direct link to just the bicycle tutorial: http://www.3drender.com/rhino/bikehtml/index.htm

To see a demo of how 1-rail sweep works in MoI, check out the video tutorials here:
http://moi3d.com/1.0/docs/tutorials.htm

That kind of tubular sweep is used in both the Sunburst and the 6-Leg Pod tutorials. If you watch those it will show you specifically how MoI's sweep function works.

- Michael