How to use other pin functionalities other than normal?

How do I use the UART functionalities of PA_09 and PA_10? this is the third functionality in the pin out.

I wrote Serial pc(D14,D15);
i got an error: pinmap not found for peripheral


Are you using the mbed compiler?
I tested it after seeing your question, but I didn’t get that error.
Make sure you have not misplaced the platform