How to place some part of code in ITCM and DTCM in stm32h745 ?

Typically you'd use the link script or scatter file to describe the regions/sections, make the code and data with __attributes__ ((section(.xyz))) and have startup or scatterloader code to copy the pieces in place.

 /* used by the startup to initialize data */
 _siitcmram = LOADADDR(.itcmram);
 
 .itcmram :
 {
 . = ALIGN(4);
 _sitcmram = .; /* create a global symbol at data start */
 *(.itcmram) /* .data sections */
 *(.itcmram*) /* .data* sections */
 
 
	 *Src/stm32h7xx_it.o(.text .text*)
	 *Drivers/STM32H7xx_HAL_Driver/Src/*.o(.text .text*)
	 *Middlewares/Third_Party/FreeRTOS/Source/*.o(.text .text*)
	 *Middlewares/Third_Party/FreeRTOS/Source/portable/GCC/ARM_CM4F/port.o(.text .text*)
	 *Middlewares/Third_Party/FreeRTOS/Source/CMSIS_RTOS/cmsis_os.o(.text .text*)
	 *Middlewares/Third_Party/FreeRTOS/Source/portable/MemMang/*.o(.text .text*)
	 
 . = ALIGN(4);
 _eitcmram = .; /* define a global symbol at data end */
 } >ITCMRAM AT> FLASH

Linker script place whole C files to the ITCM section.

Now your startup file has to copy the code from the Flash to the ITCM RAM.

/**
 * @brief This is the code that gets called when the processor first
 * starts execution following a reset event. Only the absolutely
 * necessary set is performed, after which the application
 * supplied main() routine is called. 
 * @param None
 * @retval : None
*/
 
 .section .text.Reset_Handler
 .weak Reset_Handler
 .type Reset_Handler, %function
Reset_Handler: 
 /* Enable SRAM clocks early */
 ldr r0,=0x580244dc
 ldr r3,[r0]
 orr r3, r3, #3758096384 /* 0xE0000000 */
 str r3,[r0]
 
 ldr sp, =_estack /* set stack pointer */
 
/* Copy the data segment initializers from flash to SRAM */ 
 movs r1, #0
 b LoopCopyDataInit
 
CopyDataInit:
 ldr r3, =_sidata
 ldr r3, [r3, r1]
 str r3, [r0, r1]
 adds r1, r1, #4
 
LoopCopyDataInit:
 ldr r0, =_sdata
 ldr r3, =_edata
 adds r2, r0, r1
 cmp r2, r3
 bcc CopyDataInit
 movs r1, #0
 b LoopCopyDataInitITCM
/* Zero fill ITCM ram section with source code */
CopyDataInitITCM:
 ldr r3, =_siitcmram
 ldr r3, [r3, r1]
 str r3, [r0, r1]
 adds r1, r1, #4
LoopCopyDataInitITCM:
 ldr r0, =_sitcmram
 ldr r3, =_eitcmram
 adds r2, r0, r1
 cmp r2, r3
 bcc CopyDataInitITCM
 ldr r2, =_sbss
 b LoopFillZerobss
/* Zero fill the bss segment. */ 
FillZerobss:
 movs r3, #0
 str r3, [r2], #4
 
LoopFillZerobss:
 ldr r3, = _ebss
 cmp r2, r3
 bcc FillZerobss
 
/* Call the clock system intitialization function.*/
 bl SystemInit 
/* Call static constructors */
 bl __libc_init_array
/* Call the application's entry point.*/
 bl main
 bx lr 
.size Reset_Handler, .-Reset_Handler