You can exchange data through import/ export of SimaPro CSV files, via File> Import or Export.
To transfer complete projects to another user, use the database import and export feature (File> Import SimaPro database or Export SimaPro database). Note that for database consistency, your project will be exported including the libraries and methods it is using. These libraries will overwrite existing libraries and methods at the importing user, if they are of the same name. The procedure on how to import/export SimaPro database can be found on this page.