The Ultimate Character Controller is an Editor Extension so when you import from the Asset Store it does not bring the project settings with it. After the Ultimate Character Controller is done importing the following window will appear:
If you are just getting started you should click the “Update Buttons and Layers” button. This will add the default button mappings and layer settings.
By default, the Ultimate Character Controller uses Unity’s input system which relies on the Input Manager. The Input Manager requires the button mappings (Jump, Crouch, Fire, etc.) to be created ahead of time so this dialog will add the required button mappings. It will not override a button mapping that already exists.
If you would like to perform the button or layer update later you can do so by selecting the Tools -> Opsive -> Ultimate Character Controller -> Main Manager menu option and then select the Setup button followed by the Project tab at the top.