Affiliate link to WPMU DEV

A week to 10 days ago James posted that we can set up our affiliate link to WPMU DEV so when someone clicks through any links to WPMU DEV from our site it will register as a click through and we don't have to use the affiliate link.

How do I do it?
Where do I find where to do it?

Since I upgraded to WP 3.1 a few things have disappeared.

I'll get back to the forum in about 20 hours, hope to see an answer.

Thanks in advance,