Joomla version? CB version? GJ version? Have you created categories? Are they published? Have you created groups in your categories? Are they also published? Have you reviewed in the installation manual included with GJ? Please attach screenshots of what you're seeing.
Note the above demo link is old. A more up to date demo of GJ can be found below.
cbqspro.cbdemosites.com/groupjive
Try attaching with a browser other than FF as there's a bug in FF18 that prevents attachments from working right in Kunena, no idea why. Do not attach a document with screenshots, just attach the screenshots. Press print screen and paste into Paint for example then save it as JPG.