If you have project with a lot of files and want to move those into a dataset, please go to Project > Datasets > "Create new dataset" in the Domino UI, then choose "Create by launching a workspace". After opening a workspace, start a terminal and use the "mv" command to transfer the files to the Output directory. Once that's complete go back to the workspace and sync. That should create a snapshot for you.
We generally recommend using datasets for larger projects to keep Domino running smoothly.