Your system's first boot on its own power is what electrical engineers call the “smoke test”.

If you did a default installation, the first thing you should see when you boot the system is the menu of the grub or possibly the lilo bootloader. The first choices in the menu will be for your new Ubuntu system. If you had any other operating systems on your computer (like Windows) that were detected by the installation system, those will be listed lower down in the menu.

If the system fails to start up correctly, don't panic. If the installation was successful, chances are good that there is only a relatively minor problem that is preventing the system from booting Ubuntu. In most cases such problems can be fixed without having to repeat the installation. One available option to fix boot problems is to use the installer's built-in rescue mode (see Section 8.7, “Recovering a Broken System”).

If you had any other operating systems on your computer that were not detected or not detected correctly, please file an installation report.