In the video, Stephen instructs students to create a project using an earlier Unreal Engine version to add the modular building asset pack, then port over to the new project. However, you can add the modular building assets directly, by selecting ‘Add to Project’ then ‘Show all Projects’ and selecting the first person shooter project, then selecting the version control and choosing an earlier version in the drop-down selection.
Doing this will let you click ‘add to project’ and your assets will import without the intermediary step.