Take a fabric grocery tote and put it in the bucket. I took the handles of mine, wrapped them around to the bottom of the inside bucket and secured them with parachord so the bag wouldn't move. Feel free to use whatever means you wish to secure the bag.
The bedding and worms and "canopy" (for lack of a better word at the moment) will go inside the bag. The bag allows water to drain out freely and air to get in, while keeping all the castings and bedding and compost contained.
Make sure the bag is made out of polyester! If it's made of cotton, the worms will eat through it. This wouldn't be the disaster of a lifetime, but it would potentially make more of a mess than you want.