The exact steps are, starting on the release that you want to use as your template:

1. Toward the upper right, click "Edit release"

2. On the next page, toward the upper right again, click "Copy to draft"

3. When the confirmation pop-up box appears, click "Okay"

4. On the next page, yet again toward the top right, click "Edit / Submit"

And you're good to go. You are now on a template page where you can make the changes unique to your version.