Adding earthworms to your bokashi soil factory is a great idea if you are using low quality soil or bagged compost in your soil factory. However, if you are adding good quality garden soil to your soil factory there is likely no need to add extra worms. It is the worms (and other biota) in your soil which will break down the bokashi pre-compost.
If you are adding earthworms, be careful as the bokashi pre-compost is acidic and can be harmful to worms in large quantities. Therefore make sure to add your earthworms to the top of the final garden soil layer (not in direct contact with the bokashi pre-compost).