在RailsAdmin上的列表中添加其他列值

I have RailsAdmin running for my Rails 3 app which has two models - Sale and Merchandise. There's a HABTM relationship between the two. In RailsAdmin, when a sale is added or edited, a list of available merchandises is shown in the usual fashion. However, only the "name" column of the merchandise is shown. I have another column whose value needs to be included for the list to make any sense. How do I add this to the RailsAdmin interface?I have RailsAdmin running for my Rails 3 app wh