I used attiny45 before and that's was easy, but this chip is weird,
I connect XTAL2 - XTAL1 to a Cristal 12.000Hz
STC Arduino
VCC 3.3V
GND GND
but I don't know witch legs I must use to program it!
It all starts on page 13 of your linked datasheet ISP. You connect to it via a RS232/TTL converter and usually run a loader program on the PC.
But they use PC COM "RS232/TTL" I want to use my Arduino as serial port to upload the code! 
something like this
I upload Arduino ISP to my UNO R3, then connect a capacitor 10uF to reset.
then connect pins 13,12,11,10 to my chip "digital pins"
but it seems not working at all from what I know I must choose the board!!
I search on third-party bourds in arduino website, I didn't find "STC-12C5202AD"
I tried other method by using TX-RX pins and not work too!!
can someone help me in this!!
UPDATE:
this error when I tried to uploud the code to the STC ship
Sketch uses 1,030 bytes (3%) of program storage space. Maximum is 32,256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2,039 bytes for local variables. Maximum is 2,048 bytes.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xc8
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xe0
You don't need ArduinoISP. If you want to use your Arduino as a USB serial to TTL USART bridge then you have to ground the reset pin on the Arduino and then connect the RX/TX pins to the relevant pins on the ST MCU. The datasheet does not specifically mention the STC12C5201AD but most other versions also need P1.0 & P1.1 grounded to put the ST MCU into ISP mode. You will then need a suitable programmer loaded on your PC and an equally suitable hex file to upload.
I did that too! I tried their program to upload the hex file, from what I see Arduino RX light only blinking, TX not work at all, there is no communications between them