Here's how you can upgrade your Ubuntu 12.10 system to 13.04.
1. Go to the Software Sources menu.
2. Press Alt-F2.
3. Type update-manager into the box.
4. You will see a notification that Ubuntu 13.04 is available for your computer.
5. Click the upgrade button and follow the instructions to upgrade Ubuntu 12.10 to 13.04.
For more, see the original article at the link below.