First, follow the steps to export your project package in DomuS3D as described in this article.
Once you have created the necessary files, copy them onto the same disk that has DomuS3D installed where you want to import the project. In DomuS3D, select the command "File -> Import/Export -> Import project package(s)":
From the file browser window that appears, navigate to the folder where you saved your .pjp file and select the project file that you want to import into DomuS3D. To import more than one project at a time, you can select multiple projects using CTRL on your keyboard.
This article is valid for the 2017 version and later.