Need info on how to create a sample_set in the FireCloud Basics section

I was a bit lost in the Methods Configuration section, specifically under the "Workflow Expansion Expressions" subsection. I want to be able to run my workflow on each of the samples in a sample_set, but I didn't know how to create the sample_set. It needs to be clearer that one must upload a tsv to create the sample set, etc. I'm guessing that this will be a common use case (rather than clicking launch N times) so it might be good to highlight it there.
Thanks!