On the main screen one can open the configuraiton of the controls with the icon :

In the example abouve there is already a configured control with the name "My Control".

At the bottom there is a button named "New" to add a new control to the configuration.

Usually there is only one control per modelrailway layout. For bigger layouts it can make sense to use more then one control, so there is a control for the locomotives, one for the accessories and one for feedbacks.

Acutally RailControl supports the following controls:

Manufacturer Control
CAN-Digital-Bahn CC-Schnitte 2.1
ESU ECoS/Central Station Reloaded
LDT HSI-88
Märklin Central Station 2/3 via TCP (new)
Märklin Central Station 2/3 via UDP (old)
Märklin Interface 6050/6051
OpenDCC OpenDCC Z1
Roco Z21/z21