example with MN

note how the filename and subdirs follow very close with
File name standards (and to some extent ID3 tag standards)      
with 000 left padding, all lowercase, no spacing, etc.

To get to the final "mn001" file, first we have to create a series of subdirectories to get there. For SN and KN, we would need to create subpages underneath to build out the tipitaka tree. For MN, it's a flat 152 suttas sitting under here so no new subdir is necessary. So for this example, we would start here:
then on the top menu close to right edge of screen select "+ create page".
You can actually do this example, it uses a tempname which you should remember to delete later.
under "select a template to use", pick the "sutta index entry".
we would name it "mn001_TEMP_" (don't hit return yet)
and select the option under it to "put page under <current directory>" rather than the default option of "top level".
Then push the "create page" button to continue.

It will take you to the page creation process, the template contains a checklist that explains how to fill it out.

If that sutta already has a sutta index entry page, which "mn001" does, and suppose you wanted to add another audio entry, then what do you do?

In that case, just study the "sutta entry index " template located here:
and Just cut and paste what you need from that, studying the checklist to understand what you need to change, and paste it to the existing sutta index page.