Worms can make you an ongoing supply of nutrient-rich topsoil - if you have a healthy population. The best thing you can do you help them breed is to avoid disturbing the soil too much.
You can add our garden worms as well, of course, but making your own worm compost and adding this to the soil in your garden will also encourage a natural increase in your worm population.
Or if you want more info about purchasing a wormery or starting worm composting please pop on over to https://www.wigglywigglers.co.uk/collections/worm-composting