Parent Child Configuration Help

Hello,
I'm trying to configure a Parent-Child Case relationship for our Sanitation Market App. I'm pretty confused on the P-C configuration and could really use some guidance.

We are monitoring Latrine Sales by household, so the first step in the workflow is to Register a Household, the parent case (case type : household). Next, I want to register Latrine Sales as a Child Case (case type: sales) so each latrine will have its own Case ID. There could be multiple latrine sales per household, so we ultimately want to track the construction of each latrine, which is why I'm trying to implement the parent-child configuration. My current App set up is shown in Photo 1.
Photo%201

I'm honestly a little fuzzy on the next steps. In the Case Management tab for the form Step 1: Inscription des Menage, I added a Child Case Step 2 Latrines Vendues (sales). In the Case List of Step 2: Latrine Vendue, I assigned my Parent Child Selection as shown in Photo 2

AI'm unclear on how I connect these two Cases. My intention is that once the user registers a household, they could view that list, select a household, and then register a latrine sale. I've attempted to connect these cases through my first question in the Latrine Vendues form- It asks the user to confirm the latrine sale for a given household, but I don't know how to reference the parent case (Photo 3) because the App Properties doesn't display the properties from the Household Case. I know this is because the App Properties reference the "sales" case type, so I think I just need to know what syntax is needed to reference the Household Cases (parent case). I know the syntax I shown currently is not correct.

Any suggestions for the syntax or where I might have gone wrong in my app set-up? Thanks in advance!

I’m unclear on how I connect these two Cases. My intention is that once the user registers a household, they could view that list, select a household, and then register a latrine sale.

You can make a followup form which operates on the household case, then on that form's case management screen, at the bottom, you can configure the creation of a child case. That's how the latrine cases should be registered for them to be linked together.

Have you looked through the wiki page on Child Cases? In particular, it mentions an addon that you have to enable, have you already done that?