How do I reset my password in Ubuntu without knowing it?

I recently installed Ubuntu on a virtual machine. When I made the account while installing, I made the password 2251, but now when I type the password in for installing updates, etc., it doesn’t work. It’s possible that I’m wrong, but I’ve tried every other password that I would use, and none of them work. How can I reset the password, or at least make another user account with equal administrative privileges?