Serial ports aren't showing up.

I have an Arduino Nano and whenever I connect it to my computer, the power light turns on and everything seems to be running, except I can't find the correct serial port in the tools menu. I read the troubleshooting page on this but I don't know how to check for any of the things it's telling me to do (check for programs that run all serial ports, make sure firewalls aren't blocking the serial ports, etc.) I'm fairly new to the whole thing, so i'm hoping someone can help me figure out what the problem is. I am running El Capitan on a mac book pro, but it wasn't working on Yosemite either.

Flip the nano upside down and read the marking on the chip. Post what you find.

WCH(in big type) CH34OG (In small type and beneath that is a line and then 202645801 (then on another part it says in small type)AMS1117(newline)5.0H1430 (then there are 2 yellow parts that say)A475C(new line)115C2(thank you for your help.)

OK, there it is. The CH340G is the serial port chip. The driver is here:

I've not tested it with el capitan. It's a Yosemite driver for sure. Used it on my 2008 mac before trading it in for a more recent mac at my college tech support. I'm downloading el capitan so I'll find out soon.

Thank you for your help, but it didn't work on El Capitan.

Maybe it is not a signed driver etc. I'll see if I can get it to work and post back.