Split a channel

I am going through Computer Music 03-15’s D&B Track Builder tutorials and videos. They are using Live9. One thing he did was to put an audio effect rack on the master channel, create to chains in it, load up a plug in the controlled level of mid and side indivually, then plopped on a type of limiter on each to maximize each.

I am wondering how I can do that in Cubase. I’ve only got a master group channel that I send everything through. I don’t know how to output one channel into two others, so I can control mid and side separately.

Then you need to start reading the manual to learn the basics of the program.
Sorry if that sounds harsh.
Learn about groups, how to use sends and direct routing, read up on ALL the included plugins so you understand what they do and how they can help you, download a few M/S plugins and learn what they do.

Learning and understanding the basics is the important stuff.
The rest will then come significantly easier.