Posted by Majorie,

There are two types of earthworm best suited to worm composting are the redworms: Eisenia foetida (commonly known as red wiggler, brandling, or manure worm) and Lumbricus rubellus- they are often found in aged manure and compost heaps. The use of dew-worms (large size worms found in soil and compost) as they are not hearty enough to survive the compost process.  

The bravest of composters will get their worms from a horse stable or farmer with a manure pile- you simply collect a bagful of manure with worms.  You can also get them from friends compost bins.  And, and easy answer is to purchase your worms. 

You will need approximately two pounds of worms (roughly 2000) for every pound of food you plan to compost each day.  Your worm population will increase over time, allowing you to compost even more waste.