When uploading directly from VRoid Studio to VRoid Hub, you cannot (=you don't need to) set a VRM license because VRoid Hub itself allows you to set a model's conditions of use, which are equivalent to a VRM license (avatar information, permission settings regarding the avatar's characterization, etc.).
VRoid Hub's condition of use cover all types of VRM licenses except for "Others", so after uploading your model to VRoid Hub, go to Edit model data > Change conditions of use in the lower right corner of the page and check the box that applies.
See these articles for more information.