How to Start AWS FreeRTOS in STM32F7 series MCU?

How Start the AWS FreeRTOS in STM32F7 Microcontroller ?

Sorry, but your question misses necessary details to get a matching answer, right ?
The Stackoverflow guidelines How do I ask a good question ? are very good and will help you.
In your case it’s not clear if you have problems to start a FreeRTOS application or if you want to start developing such an application.
Assuming the latter ST ARM Cortex-M7 STM32 F7 RTOS Demo is a good starting point.
Guessing you’re using Cube there is a doc provided by ST which could be helpful:
Developing applications on STM32Cube with RTOS

One thing to take into account is that FreeRTOS is not a ‘stand alone’ operating system (like Linux or Windows or even DOS) that you load on a machine, and use to load and run applications, but is an embedded operating system that is embedded is a particular application and provides that application with services, namely allowing the application to be divided into tasks, and the communication methods between those tasks.

The simplistic answer, is to call vTaskStartScheduler(), like you do on all platforms.