BuddyPress.org

BP requires pretty permalinks. Go to Settings > Permalinks and set permalink to other than what’s there on default.

>> Is there something I need to change in Apache config

mod_rewrite must be enabled in your server https://codex.buddypress.org/getting-started/before-installing/#system-server

info at http://www.coolestguyplanettech.com/fastest-way-to-install-wordpress-on-osx-10-6/
or info with mamp http://soderlind.no/archives/2011/08/26/running-wordpress-locally-on-mac-os-x-lion/

Google of no help??!!

http://www.google.co.uk/search?client=opera&rls=en&q=.htaccess&sourceid=opera&ie=utf-8&oe=utf-8&channel=suggest

any of those pages will help you understand what an .htaccess file is and where you may find it located – I would suggest that actually unless you have a real desire to learn how to configure standalone web servers on osx you install a LAMP package from the likes of Xampp:

http://www.apachefriends.org/en/xampp-macosx.html

Or MAMP as mercime has suggested/linked to.

Please make sure that your WP installation has been set up properly – pretty-permalinks included – before installing BuddyPress. In this vein, please post your mod_rewrite issue at the proper forum https://wordpress.org/support/forum/localhost-installs