How to download Macaulay2 for MacBook Pro?
Homebrew needs your Mac password because installing most SW (including homebrew) requires permission from an admin user, which is given by you entering your password.  Just enter the same password you use when you log into your Mac, and homebrew should get installed.  Then, you can type brew install Macaulay2/tap/M2 to install it.
UPDATE: According to https://faculty.math.illinois.edu/Macaulay2/Downloads/MacOSX/index.html you can also download the SW on a disk image and just drag the Macaulay folder to the Applications shortcut in the disk image, like this:

Then follow the instructions in that ReadMe file to complete the configuration steps needed to use this SW.  This will allow you to use this SW on your Mac without any need for homebrew.