Cannot execute this binary file appreciate any assistance, I'm a Mac Noob

Im trying to upgrade MySQL in MAMP to 5.6 according to the these instructions

When I try to run the .command script as per #2 I get the following output:

Sandies-MacBook:~ sandie$ /Users/sandie/Downloads/Install_MySQL_5.6.25.command ; exit;
-bash: /Users/sandie/Downloads/Install_MySQL_5.6.25.command: cannot execute binary file


I have found this post, but I still get the "Cannot Execute" error.  I checked the file type as per the instructions, and the result is:

Zip archive data, at least v2.0 to extract

The instructions suggest I need to unzip it but I have no idea how?

Any help appreciated :)
Remote/delete the downloaded file
Download it again, it should get a .zip extension
Double-click the downloaded file to unpack it
In Terminal, run 

cd ~/Downloads
chmod +x Install_MySQL_5.6.25.command
./Install_MySQL_5.6.25.command