I think I have found the answer to my own question. It seems one can include the Ambiq code for Fast GPIO by:
// Including the Ambiq gpio library
#include <am_hal_gpio.h>
#define _clockPin 37
....
// Initialize fast gpio where the HEX number is the pin map for the fast gpio pins i.e. pin 37 as an output
am_hal_gpio_fast_pinconfig((uint64_t)0x1000000000, g_AM_HAL_GPIO_OUTPUT, 0);
am_hal_gpio_fastgpio_enable(_clockPin);
...
//then use
//digitalWrite(_clockPin, HIGH);
am_hal_gpio_fastgpio_set(_clockPin);
//digitalWrite(_clockPin, LOW);
am_hal_gpio_fastgpio_clr(_clockPin);