It has great instructions for installing directly from source and you don't really need to be familiar with ruby to install it. It requires some standard components (web server, database) which should exist on all servers and then you follow the instructions and presto! You have your own gitlab!! It also has great upgrade instructions so you can always be up-to-date.
I know gitlab can also be used through the cloud version (and it even has free private repos) however some organizations feel better if the source code of their projects stay inside the organization.