STEP 1 To compress a file, you will first need to download and install Winrar, which has been explained in the "Installing Winrar" section of this tutorial.
If you are wanting to compress a file, you need to first find the file and then right click on it. This will bring up a small menu that will be to the right or left of your cursor. In this little menu, you will need to select "Add to archive"
STEP 2 A new window will appear, which will ask to setup how you would like the file to be compressed. You do not really need to change anything in this window, but you can change weather the file is a zip or an rar by selecting one or the other from the "Archive format" Other then this, the only real thing you need to do is click the "OK" button.
STEP 3 After pressing the "OK" button, your file should be compressed and located in the same place that the existing file is. You will note that there are now two copies of this file, one that is compressed and the one that is not.