I think DesignSpace has moved on a few revisions since I last used it but, from memory, if you have a solved analysis then either:-
(a) click on any constraint in your "model tree" and the reactions are reported in a sub-window somewhere
or
(b) right click on the constraint and it will give you an option to display them.
If the GUI has changed drastically since I last used it though I could be wrong, but I suspect it's something along these lines.