The ''Add Files '[ALT+A]' button may be used to add file as explained under  New [F2] section.
Once files are added and the project is saved, the saved single project file will contain all the file configuration ,properties,registry setting,password setting,dialog information etc.It may be noted that if the project file is used in other machine the connected setup folder file will be required to open the project file and if there is change in the source path, Smart InstallBuilder(8.2) will be unable to load project file and in that case reload the files as a new project explained under
New [F2] section or copy the original project folder to the root of any of the drive in the new machine and open the project using Smart InstallBuilder (8.2).