How do I use X sample pipeline?

From Navigation panel :  Build → Sample Pipeline → Click on Pipeline of interest  → Create a pipeline from Sample 

Click Build > Sample Pipelines in the Navigation panel to view the sample pipelines. Click the name of a sample pipeline to open the pipeline in the pipeline canvas and explore how the pipeline and stages are configured. You can also create a new pipeline from the sample pipeline to use the sample as the basis for custom pipeline development.

https://docs.streamsets.com/portal/platform-controlhub/controlhub/UserGuide/SamplePipelines/SamplePipelines_title.html#concept_wms_j5t_1jb