How should we introduce a puppy to a wheelchair?

my Uncle is in a wheelchair and i do the training with the puppy...hes a Shetland Sheepdog Border Collie mix...his father was a therapy dog and the woman had an accidental litter with a rescue dog that was in a silent heat...anyways...ive already trained him a lot of things but i want to know how to train him with my Uncles wheelchair...its really not like a regular wheelchair tho...its one of those motorized wheelchairs. i need to train the puppy to walk along beside the wheelchair but not to fear it...does anyone know how to go about this?