The first step is to walk with him and the bicycle together.
We've had a few successful walks so far. He managed to keep going without stopping and sniffing for a whole block!!! (1/10 of a mile = almost 1/5 of a km). He barely notices the bicycle at all. His speed is inconsistent but I think I'm a bit inconsistent too. It's hard to wheel a bicycle around and grip a leash with a 50+ lb pitbull in tow.
We'll do a few more walks before I start pedaling... I think my Brompton is the best bike for this task because the low frame is easier to step through and mount, or dismount.
I'll post photos when we have third partner available, unless I can train Barnaby to take photos too. :)
Meanwhile, here's a great resource for all manner of dog/bicycle travel.
UPDATE - I pedaled with him around the block. He loved it! I've been going to slow for him with the walking, the jogging... cycling is much more fun!