First, if you have a wired USB keyboard, plug that into a USB port and see if it works.

 

If it does, plug the USB dongle for your wireless keyboard into the same USB port - it should work as well. If not, it may be the brand of wireless keyboard that is the issue (check if the wireless keyboard works in a laptop or desktop PC by plugging the dongle into that). I find Logitech to be the better brand of wireless keyboards/mice for compatibility.