Once you have followed the download links you will be required to log into your Salesforce Organisation where you will be presented a screen similar to the one below.
A list of components to be installed can be viewed using the View Components link.
Select Install for All Users and click Install.
Install complete.
Next Step
Customize Contact and/or Lead Page Layout (Version 3.x)
or
Customize Contact and/or Lead Page Layout Lightning (Version 3.x)