Port Not Being Found
Try this...
Go to your Arduino IDE.
Under the Tools tab, go to "Board" and select Arduino Leonardo.
Then in the Tools tab, go to Port and check to see if a port is selected.
Use this link to try and find which Serial Port you should have: https://www.arduino.cc/en/Guide/MacOSX
Try plugging in the cable in different USB ports on your computer and see if the port number changes automatically.

Also, could you please say what peripherals or other things are connected to the arduino? Because for example, I know what using a Bluetooth slave with the Arduino while connected with the cable to your computer, doesn't let you upload your program. There could be similar problems to this.