So you have managed to successfully install and boot Ubuntu. Congratulations.
Gnome Display Manager (GDM)Edit
The first thing you will see when you boot your new operating system is the Gnome Display Manager (GDM), your login screen. In the box you should enter your username which is the name you chose during the installation process. After you have entered your name press the enter key. You will then have to enter your password which you also chose during the installation process. The password will appear as black circles so that nobody can see your password. After you have typed this press enter and voila, welcome to Ubuntu!