Compressing a File
First right click the file you would like to compress. Hover over "Send to". Click on "Compressed (zipped) folder
This will send the file into a zipped folder that will be smaller than the original file.
This folder can then be sent to another recipient that can then uncompressed the file and use it.
Uncompressing a File
First right click the compressed folder. Then click "Extract all".
A popup will appear.
You will now have an uncompressed version of the file!