New PCB with ATMEGA328P

Hi,

I designed open firmware board with ATMEGA328P-AN, made a new Arduino shield using Rx,Tx, GND and RESET pins via a cable in order to programming the ATMEGA328P-AN. I removed the ATMEGA328P chip from the original board and tried to download sketch into external PCB. After countless programming attempts, Googled in order to see the problem. I found few articles, if I understand need to download bootloader into external ATMEGA328P-AN, then Arduino IDE should download the sketches.  But the PCB manufactured, I wasn't aware that need ICSP connector on the PCB. Now is there an option to download the bootloader via Tx,Rx of the serial UART?

Thank you,