Can't figure out how to use snapshot to compare

Okay, I’ve watched the tutorial, and I’ve looked in the manual.
Here’s my problem. Tell me what I’m doing wrong.
I created a document.
Then I created an alternate of the same document.
Let’s just call them doc_one and doc_two
So, I take a snapshot of doc_one.
I want to compare it to doc_two.
So I go to doc_two and take a snapshot of that.

Now, how do I compare them, when only the snapshot of the last doc snapshot-ed appears in the list of snapshots?

If I select doc_one in the binder, I’ll have doc_one in the editor, and doc_one is the snapshot I see in the snapshots list.
If I select doc_two in the binder, I’ll have doc_two in the editor, and I’ll see doc_two in the list of snapshots.

The fellow with the cute (australian?) accent in the tutorial is looking at two versions of the SAME doc.
What do I do when I want to compare two different docs. Can I?
What am I doing wrong?

That’s not something you can currently do. You can compare differences between snapshots and any snapshot and the current version of a document, but you can’t compare two different documents, or snapshots from within those documents to each other. To do this, you’d need to snapshot doc_two, then paste the contents of doc_one (or the snapshot you wish to compare) into doc_two, and then run the comparison.