First off, the toolset will not do it. You have to do it by hand. You can open the DAZIP up in most any archive program. It is just a ZIP file renamed. Once you open it up, you just need to create some folders for the new content and then add your override files. The archive will alrady have a "packages/core" folder. In "core" just make a new folder, "override". If you want the package to be properly compatible with DAModder, then inside that "override" folder, create one more subfolder with the UID of your mod. So it will look like "packages/core/override/uid" Inside that, place your override files.