As the plants are in dormancy and lack leaves in winter, they have no ability or need to photosynthesize so require no light. Provide only enough water to keep the soil barely damp.....lack of leaves also means they don't transpire much either.

"do they have to receive sunlight?" No, not until the spring.

"can they be overwintered in the dark?" Yes, you can overwinter either in a basement, a shed or a garage.

"how often will I need to water them, if at all?" That depends on your winters, shrub size, pot size, etc. In some locations, they lose humidity faster than in others so test the soil moisture and water if it feels dry. You may not be able to insert a finger through the soil if the soil has frozen though. Consider wrapping the pot with insulating materials like burlap to help retain warmth. But generally speaking, it may be more practical to wait to water until temps are above freezing or until the soil thaws. I typically water about monthly in my garage, maybe a cup of water, but it may require more/less in your place. Consider maybe increasing the amount of water if you have to water twice in one month?

https://www.youtube.com/watch?v=byhev9unWTQ