Slice the meat from the bones. You can dice the meat if you like if you know you are planning to use it in a recipe that calls for cubes of cooked turkey.
Place the turkey on a parchment or foil-covered baking sheet in a single layer. Transfer to the freezer for 1 hour, until the turkey is quite chilled and firm. This will allow the slices or cubes to stay separate when you freeze them in a bag or container. Or, tightly wrap whole pieces of turkey in layers of plastic wrap to create a bundle.
Label a freezer-proof bag or freezer-safe container with the kind of turkey you are freezing (dark meat, sliced, cubed) and the date. Use a permanent marker like a Sharpie.
Transfer the turkey to the labeled freezer-proof bag or container. If using a bag, press out any excess air. Put the turkey in your freezer and freeze for up to 6 months.
Notes
Leftover cooked turkey freezes well for up to 6 months if properly handled, packed, and frozen within 3 days of the original preparation. However, I like to try and use it within 3 months for the best flavor and texture and to avoid the possibility of freezer burn.