I have forgot my main password for main log in and for everything that I need to authenticate things for.
How can I recover or reset my password?
You cannot recover the password, but you can change it to log in again.
When you boot, hold down the Shift key until you get the Grub menu.
Choose the item (usually the second one) that reads, "Ubuntu, with Linux ... (recovery mode)".
When it boots, select the option "root -- Drop to root shell prompt".
You will see a flashing cursor. Type the following and press Enter:
but replace "user" with your username. Type the new password when prompted (twice).
Then press Ctrl-Alt-Delete to reboot normally.