Changing components in circuit tree is quite simple. Add the peripheral you wish to add in the board. Now click on the icon placed above the library component to open the pop up block.
In the pop up form you will need to select function and press get parts button to allow part selection for the processor. The application will take few seconds to select a component from the library and propose other alternatives. You can click upon the select matching parts and scroll through parts.
The component to be selected can be done by clicking on the radio button as shown below