My MacBook is asking for a password but I never established one. I cannot get passed the password screen

See if you can create a new administrator account by restarting the Setup Assistant:

1. Boot into Single User Mode: Start/restart your Mac. As soon as you hear the startup tone, press and hold ⌘ + S until you see a black screen with white lettering. (If you end up back on the login screen after a flash of the black screen with white lettering, enter your password and it will return to the black screen.)
2. Check and repair the drive by typing /sbin/fsck -fy then ↩ enter - as directed by the on-screen text.
3. Mount the drive as read-write by typing /sbin/mount -uw / then ↩ enter.
4. Remove the Apple Setup Done file by typing rm /var/db/.AppleSetupDone then ↩ enter.
5. Reboot by typing reboot then ↩ enter.
6. Complete the setup process, creating a new admin account.

Be very careful to notice the spaces in those Terminal Commands.

Once you've done that the computer reboots and it's like the first time you used the machine, except all your data will still be there. Your old accounts are all safe. From there you just change all other account passwords in the account preferences!!

Or...

Reset Admin Password…

Use the Recovery Partition — Starting with 10.7 Lion, which was sold only through the Mac App Store, the installer disc was replaced by the Recovery partition, a small chunk of the boot disk that contains a stripped-down version of Mac OS X and essential utilities. To reset the administrator password when running Lion or later:

1. Restart the Mac while holding down the Option key, and double-click the icon for the Recovery partition. A Mac OS X Utilities screen appears.
2. Choose Utilities > Terminal.
3. In Terminal, type resetpassword. Rather unusually for a task performed from the command line, a graphical Reset Password window appears.
4. Select the startup volume at the top of the window, and then choose a user account from the pop-up menu. In the fields below, enter the new password, confirm it, and add an appropriate hint.
5. Click Save, and then choose Restart from the Apple menu