To Install any of the Icons for AIM, simply click on the one to the right that you would like to install and it should do so automatically.

If this doesn't work, try right-clicking and saving the icon to your computer and adding manually when Instant Messenger is open.

Yahoo Messenger

To install any of the Icons to the right for Yahoo Messenger, simply right-click and save the icon to your computer and add them to Messenger when it is open.

This is a link to Yahoo Messenger's help page should you have any problems.