Making A .zip archive
To make the zip file, you need to be in the Finder (the menu to to right of the Apple menu needs to say "Finder").
To get there, you can click on the Finder icon in your dock
Once it says Finder at the top of the screen, find the file you want to make an archive of (likely in your Documents folder), and click on it once to select it.
Once you have it selected, choose "Create Archive Of..." from the File menu

A .zip file will be created somewhere close to the original.
This .zip file would be what you would add as an attachment to your email