Even though the scope of SAP HCM, in terms of Enterprise Structure, is to configure 1) Personnel Areas, and 2) Personnel Subareas, but there are other elements which need to be configured as well, including the Client, Controlling Area, and Company Code.
The SPRO nodes provide detailed documentation on how to set-up these elements which you can refer to configure the FICO related structure. However, as you are working in a group, your Finance colleagues have to set it up for you.
You’ll need these when you assign the Personnel Area to company codes. The assignment of company code to other financial organization will be done by your training colleagues.