What are the necessary configs for using domain mapping on an addon domain?

1. I have installed WordPress Multisite on the following address public_html/schooledge.com.ng which is clearly not the RootDirectory but an AddOnDomain. Are there additional configs that I need do?

2. I also understand that my users need only point the their ARecords to the IP address for the magic of mapping to happen and there is no need parking their domains.