I am trying to install something and it is asking for my computer password. I thought I knew it and nothing works. Hint doesn’t jog my memory. What can I do?
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The method to reset your computer's password depends on whether you've allowed your AppleID to control the reset. Normally I don't recommend people enable this feature but here's a few things to try.

Try your AppleID password.
Try the word "password" just in case I changed it in the past working on your computer. I only ever use the word "password" if I ever have a need to change a client's password and I always use the same word: "password".

If you need to reset your password, there is a way but it comes with consequences. Your keychain (all your other passwords like email, websites, etc..) will be reset and you'll have to re enter all those passwords again for your computer to start a new record. This is done for security reasons. You wouldn't want someone to steal your computer, reset your password, then have access to all your other passwords.

So to reset, you can try the following. Start the computer in recovery mode by holding down command+r at startup. Once booted, in the menu bar, open terminal. Type resetpassword then hit return. You will see an application open that will allow you to choose your user. Enter a new password (twice) then restart the computer. If you've enabled FileVault however, you can forget it. This method will not work.

Before trying this I do encourage you to exhaust your guesses. There is no limit to the number of times you can try your admin password. The terminal method should only be used as a last resort. Most of the time, if you sleep on it, you'll get it eventually.