You will want to be able to selectively chose which links you want to apply the attribute to because you don't want to apply a "nofollow" to a legitimate link within your site or to another page used for reference or another such link. A link that you do not apply a NoFollow attribute to is called a DoFollow link. Yeah...go figure!

I use Title and Nofollow For Links which can be found by searching in the Add New Plugin options within your Wordpress site. Another very popular one is Ultimate Nofollow WordPress plugin. I will use the example from Title and Nofollow for Links which is what I use. Once you have located the plugin of your choice and installed it and activated it you will be able to selectively chose "nofollow" or "dofollow" links without having to go into the plugin settings. This first example is using a “dofollow” link. To review, that would be any external or internal link that is not an affiliate link.

This example show a “nofollow” link which points toward an affiliate link.