Here you can freely create a Team for College Football 23. Make sure, when creating your team, create the team to be realistic as possible and your university/college team has to come from an existing location, there is an example as well.
When adding your team to a conference, you can either create one or add your team to an existing conference. An example would be adding your team to the Southeastern Conference (SEC), Big Ten Conference (B1G), Pacific-12 Conference (PAC 12) Atlantic Coastal Conference (ACC), etc.