I can't remember my passcode and need to change it. How do I change my passcode. I am at my home with my Mac computer and iPhone

See this article > If you forgot the passcode on your iPad, or your iPad is disabled

I just got a new Mac computer and had set it up so there was no need to sign on each time. Something happened and now I can't get into my computer without a password and I have no idea what it is. How can I find out my password or reset it so I can access my computer?

See this article > If you forgot your Mac login password