Well if you have a plug on the back of your PC Which looks like this:
Then all you need to buy is a USB Keyboard and mouse which you can get online or a local computer store then you simply plug them in!
If you dont have any of those plugs,you should get a USB Controller card.
A USB Controller Card looks like this,
Now you can buy these off the internet or from a Local Computer store.Now you should open your computers case and check if you have any PCI Slots empty,they look like this:
Once you purchase one,you simply install the card as shown in the manual,and then install the correct software,and then you can use a USB Keyboard and mouse Because if your PS/2 Port is bad,there is no real way of fixing it.