How do I write directly to regiters in Mbed (set the GPIO voltage to 3.3V)

[LEDguy (John Gray)]

1. I would like to set the output of my GPIOs in my nRF52840 to 3.3V instead of the default 1.8V.
2. I have found a register called REGOUT0 that needs a value of 5 to be set.
3. I also found a structure called NRF_UICR_Type containing the
   typedef struct {
   __IO uint32_t UNUSED0;
   __IO uint32_t UNUSED1;
   __IO uint32_t UNUSED2;
   __I uint32_t RESERVED0;
   __IO uint32_t UNUSED3;
   __IO uint32_t NRFFW[15];
   __IO uint32_t NRFHW[12];
   __IO uint32_t CUSTOMER[32];
   __I uint32_t RESERVED1[64];
   __IO uint32_t PSELRESET[2];
   __IO uint32_t APPROTECT;
   __IO uint32_t NFCPINS;

__IO uint32_t DEBUGCTRL;
__I uint32_t RESERVED2[59];
__IO uint32_t DCDCDRIVE0;

__IO uint32_t REGOUT0;

} NRF_UICR_Type;

I just don’t know where to read and write the structure!!!

Can anyone shed some light on this??