Different manufacturers give different instructions – basically you need to get them very hot while braking – multiple stops from speed. However some seem to bed in easily some take a lot of work to do so. Hopes seem to be in easily.
I pedal downhill with one brake on releasing when the speed drops and braking again as you come up to speed – do each brake separately. Half a dozen times each brake – get them really really hot.
You can tell from the feel when they are bedded in as the lever should feel firmer (maybe) and the brake works more efficiently. I have also done it simply by dragging the brakes down a hill slowly – but that was on the tandem that works the brakes harder.