two of those pads are common ground(I believe upper left and lower right). The other two are not common to each other (I don't think), but they both need to be connected to the common ground in order to produce a button press.
In other words I think there are 3 connections that need to be made. KingMike_OS needs to confirm this tho, because I am only remembering what he told me and it could be that only 2 pads were needed. when we did wii rapid fire development, he did the electrical on that one.