Ohanah comes as a zip that contains package with all the things that are required for Ohanah to work (component, modules, dependancies). Installation is done via Joomla Extension manager in a standard way.
Ohanah v3 cannot be installed over the Ohanah v2. Read more here.
Ohanah v3 is not compatible with DocMan 1.x. Apart from that, there are no known problems with other extensions.If you use CloudFlare, please read this