Bryce doesn't do true HDRI but the same effect can be acheived by faking it in Bryce. Create a shpere and make sure it encases your entire scene (most like using a size of about 2000+ cubed). Now apply your HDRI image (also known as a light probe) as a texture to the sphere, put a marble in both the diffusion and ambience color in the material editor and make diffusion and ambience 100. You can also make it slightly transparent if you want an outside light source to cast shadows on the scene. Objects in the scene with reflection applied to them will be lit by the reflection of the image of the sphere.