You need to manually edit each link to add it in once the pin is up on pinterest. Having said that though recently I noticed that the pins of mine with the referral links were not loading and were coming up with error messages. I started a forum thread about this to warn others and I went through to delete all the links. So my advice is don't bother. Too unpredictable. Lots of hubbers don't and for the time that mine were working I never had a sign up despite lots of traffic.