There are two ways.
1. Right click in the article view (the central component), you'll see a list of all dictionaries that have the translation of the current word. Then just select the one you need.
2. In the
development version of GoldenDict there is a new component, called Results Navigation Pane, that provides the same view and it could be permanently shown as a sidebar:

Clicking on the dictionary name in this sidebar would allow to jump to the particular dictionary.
P.S. Also, the following shortcuts are *very* handy and I use them a lot: Alt-Down and Alt-Up - jump to the next/previous dictionary in the article view, so that there is no need to scroll, just quickly navigate down and up between the results.