The first thing you should do before installation is to make sure you've the right version of php, MySQL etc. Check the screengrab to see the right version.
Here, with my skills and knowledge, I've learnt how to install the beta 2 properly...elimination one major error making your Joomunity installation working. Just follow the steps:
1) Download the V4 com installer from www.joomunity.org (Click com_joomunity-installer.zip to download) and then install it from the Joomla back end as a standard Joomla component.
2) Now go to the Components and use one of the mirror sites given to install Joomunity or to install manually, download joomunity.zip from joomunity.zip and then, as seen in the picture, chose the path to the file in your PC. Voila you're done installing. (Read till the end, there's one more thing to be done...)
You may be confused about the other 2 files, joomunity_11217.zip (2.96 MB) and joomunity_11218.zip (2.96 MB). Many people find it confusing. The file joomunity_11217.zip is the old beta 1 [ensemble] version, while joomunity_11218.zip is the new version also mainly used for installation using the old version of com_joomunity-installer. If you are making a fresh install, which is the best thing to be done, you should download V4 com installer and install joomunity following the steps above.
One important things is that, most probably, while going to your "Edit profile" link, you may encounter an error as below:
Fatal error: Call to a member function model_contact_view() on a non-object in www/components/com_joomunity/applications/Profile/profile.php on line 90
Edit your component/com_joomunity/applications/Profile/profile.php file commenting line 89 to 92. Below is the code section
$cmodel = $this->joomunity->get_instance("contacts", "model");
$c = $cmodel->model_contact_view($id);
unset($this->joomunity->contacts);
$tabHTML->add_tab(JText::_("JOOMCONTACTTABTITLE"), null, $c);
Or one other method is, just replace the above profile.php file with the old profile.php file from the old beta 1 version of Joomunity.
I guess your Joomunity installation must be working by now. Enjoy being social!!