Steps on how to enter recovery mode can be found here
Once in the recovery menu, select root with the arrow key and then press enter. This will enter a terminal session with root access. It is then possible to reset your password via the following command:
passwd {your username}
If you do not know your username, you can find a list of the users by typing in:
ls /home
You will then be prompted to enter your new password and then again to confirm the new password.
Then type reboot and press enter to restart the machine. Then try again to login with your new password.