[ubuntu] Erasing A Thumb Drive For Installing A Newer Version OS

I have a thumb drive with Ubuntu 13.04. I used that to install it on my current machine. It holds 4 GB of data. I want to put an updated version on it. When I go to use the Startup Disk Creator program it has a button to erase the disc. I tried it and it gives an error message. Thus it won't erase the thumb drive. Can somebody tell me how to remove the data on the disc or how to write information over the current data so I can put a newer version of the OS on it?

Thank you.