My MacBook won't log me in, asking me to enter a password from August
To access the terminal you must first boot in recovery mode. Immediately after pressing your power button (your mac must be off prior to this) you should press both the Command and R keys together.

As for the password, I presume that you cannot log in at all. You can try to change your password in different ways. This is the official Apple Protocol here:
https://support.apple.com/en-gb/HT202860

You can also refer to this post:
Resetting password for Macbook

Best of luck