Does anyone know how to use Custom Fields in 2.9.9.3?

[inoculated]

I've been at it for days and I'm getting nowhere. 

I'm making a demo site so I can make templates. Just need generic products and whatever custom fields that are commonly used - dropdown to choose size, text fields, whatever. I've been messing around with them, trying each custom field type with all sorts of different combinations of settings, but they're all useless from the frontend. Every single field type results in plain text in the frontend, nothing is editable, nothing can be chosen from a list of anything, nothing nothing nothing.

It looks like 2.9.9.3 is very recent? So documentation/tutorials for this version of custom fields dont exist yet? It looks like that sticky is still under construction...
Or is there a resource somewhere that I'm missing? Everything I find wants me to use the "Cart Variant" type, but that doesn't exist anymore. Nothing is relevant anymore.

Does anyone know how custom fields work or do we have to wait?
Why are they such a mystery? This has been a nightmare.

[balai]

In the custom field you must enable both "cart attribute" and "cart input" to have them selectable

[jenkinhill]

http://docs.virtuemart.net/tutorials/product-creation/81-product-custom-fields-without-stock-control.html

The best way to get started with customs is to install the sample products & look through the customs set up for those products.