ClicketyClacketyClic I had to do the same thing recently.
To install flarum on a CPanel, you should first access to SSh and install Composer for php.
There is mutltiple tutos on the web for this but i took this one.
Then for integration, you have to install flarum in subdomain according 010101.
For this, you must first follow installation guide and then follow instruction for the SSO plugin and how to implement it.
It's not a trivial matter, hope that will help.