A suitable expression would be to make more accessible.
accessible
easy to approach, reach, enter, speak with, or use.
Alternatively, for a more informal flavor, you can use idiot-proof.
idiot-proof
built, organized, written, etc., in such a way as to be usable by or understandable to any person of average intelligence or skill: an idiot-proof camera.
This may seem a tad condescending if taken out of context, but your mileage will vary. It is listed as an adjective but I think that it can be used as a verb as well, e.g. "We should idiot-proof the user interface." Please don't use this term when talking to clients/people you don't want to piss off.