Enable USB send and receive in STM32F103C8T6

Hi all

i have a problem with read sent data from PC host client. in fact i can send data from Micro to PC host client and it can receive sent data but i can't reply to sent data to Micro via USB. i searched very well in this forum and other mainly forum. please tell me how to read data in main(void) from PC host client after sent data.

Best Regards

Ehsan Farahani Asil