Setting Up My First Network Site

I haven’t felt so frustrated, or like such an idiot noob, in a long time…

I have the sense that WordPress Multisite in general, and WPMU specifically, could help make my life as a webmaster a LOT easier. And some of the plugins look amazing…

However, I can’t find coherent, up-to-date information all in one place, and it’s very frustrating. I don’t know what to do first.

I have created and tried to install the same new domain as a network site at least 5 times now. I have removed it in defeat that many times, too.

Can someone please help me get started? Like, do these things, in this specific order?

The background:

I have shared hosting through SiteGround – one primary domain, and the hosted domains show up as sub-directories of that domain in cPanel > File Manager.

The primary domain is the multisite installation.

I have the WPMU DEV Dashboard and Domain Mapping plugins installed, including the changes regarding sunrise.php.

I have a new domain registered at GoDaddy, and pointed to the same DNS server as the primary domain (the multisite installation). I can change that, if necessary.

What are the next steps?

If this is available somewhere else, I will cheerfully go follow the directions, but I haven’t found it in two days.