Macbook

Look in the root directory for the Users folder. In it will be your Home folder. The name of it is your username. If you don't know your password see:

Forgot Your Account Password

For Lion or later

Reset a Mac OS X 10.7 Lion Password

OS X Mountain Lion- Reset a login password,

OS X Mavericks- Solve password problems,

OS X Yosemite- Reset a login password.

El Capitan Password Reset.

macOS Sierra-Reset a login password.

Change or reset the password of a macOS user account - Apple Support.

For Snow Leopard and earlier with installer DVD

Mac OS X 10.6- If you forget your administrator password,

OS X- Changing or resetting an account password (Snow Leopard and earlier).

For Snow Leopard and earlier without installer DVD

How to reset your Mac OS X password without an installer disc | MacYourself

Reset OS X Password Without an OS X CD — Tech News and Analysis

How To Create A New Administrator Account - Hack Mac

Try this:

How to Create a New User Account if You Cannot Access Your Admin Account

Reboot the computer. At the chime press and hold down the COMMAND-S keys to start into Single-user Mode. You will boot to a black screen with scrolling white text, release the keys and wait until it finishes. Enter the following lines at the command prompt pressing RETURN after each:

mount -uw /

rm /var/db/.applesetupdone

reboot

After you reboot the computer you will be taken to the Setup Assistant. When you get to the point where you are asked to set up your new user account, create a new admin account. Be sure to name this user account something different than the admin user account that already exists on the system. When you finish the Setup Assistant, it will automatically log you into the new account.

You can transfer your files from the old account to the new one. See Transferring files from one User Account to another. Once you have moved all your files into your new account, you can delete the old account using Accounts or Users & Groups preferences.

Did each command line run OK or return errors? You could try what's in here: How To Create A New Administrator Account - Hack Mac.

The last thing should have removed your setup is done flag forcing the computer to boot into the Setup Assistant so you could create a new account. If you type it in then you may have made an error with spaces not included. The first line is "mount -uw /" with a space after "mount" and another after "-uw." The second line has a space after "rm" and a period (dot) at the beginning of applesetupdone.

mount -uw /

rm /var/db/.applesetupdone

reboot