unitypackage into your existing project by double-clicking on the unitypackage file or dragging it into Unity editor Project view. from 4.0 to a newer 4.0 package), you can follow the steps below: When upgrading to the same major and minor version (e.g. from 3.8 to 4.0), please see the spine-unity documentation page section on updating. When upgrading to a different major or minor version (e.g. You can find the necessary documentation here when obsolete methods have been replaced with new counterparts.