Usb to serial diy converter

I’m trying to use a usb to serial converter like ones on ebay, to program and communicate with the serial monitor. I want to use d sub 9 the comes from usb(usb-serial converter). Is this possible for use with arduino, and what pins go were?

If your converter ends with a 9-pin D connector then no, that cannot be directly used with the Arduino. The output of that device is standard EIC-232 voltages (+/- 10V ish). You would first need to pass the signal through a MAX232 (or ADM232, HIN232 etc) chip to get TTL levels out of it.

If you don't you will blow up your Arduino.

You should be using a USB to TTL serial adapter instead. They are dirt cheap (around 2-3 dollars) on eBay and look like a small PCB with a USB port on one end and a row of pins on the other. If you get the FT-232 based version you can connect it up TX->RX, RX->TX, and DTR->RESET via a 100nF capacitor. If you get the PL-2303 version, then you only get the TX and RX to connect, so when it comes to programming you will need to press you reset switch at the right time.

Anything with a d-sub connector is probably using RS232 signaling and would need to be converted to TTL serial signaling before it is safe to connect to your Arduino.

There are readily available and inexpensive USB-to-TTL-serial converters which do exactly what you need - most hobby sites that offer Arduino hardware and clones will offer something suitable, and they only cost a few bucks. The only gotcha is to ensure that the TTL voltage level of the converter matches the voltage of your board i.e. 3.3V or 5V.

ETA: or in other words, what Majenko said.

If I'll need a voltage shifter or chip then I'll just buy one online, or use an isp.