You can easily wipe the newly created system and install again. Before performing either of these options it's best to make sure that backups of any important files (that can't easily be replaced) from your computer are current.
If Ubuntu is the only installed OS then just boot from the Ubuntu live CD/DVD/USB and run the installer again, then tell it to install to the entire disk (overwriting all existing OSes, which happens to be just the Ubuntu system you already installed).
If Ubuntu is not the only installed OS and you want to keep the other OS, boot from the Ubuntu live CD/DVD/USB. Choose Try Ubuntu without installing (not Install Ubuntu). When you have a usable desktop, run the GParted Partition Editor by pressing the Super (Windows) key or clicking the Ubuntu logo at the upper left corner of the screen, and typing
gparted. You'll see an icon for GParted come up. Click that icon.
Assuming Ubuntu is the only GNU/Linux distribution you have installed, which is probably the case, any
ext4 partition belongs to the newly created Ubuntu system. There should be just one of each. Remove those partitions in GParted. Click the green check mark to apply your changes. Then quit GParted and click Install Ubuntu (it's one of the icons in the launcher). Now install Ubuntu alongside the existing operating system to start over.