After enabling the Use Spherical Limits property in the AnimDynamics Details panel, you can use Add (+) to create an Index where you can set up sphere limits. Within each Index you can set a Driving Bone to act as a reference point for the location of the sphere and the offset its location on the X, Y, and Z axes, with the Sphere Local Offset property. You can also set the sphere's Limit Radius to determine how large the sphere is, and set the Limit Type to decide how the sphere interacts with the Skeletal Mesh.