Clone it :
git clone https://github.com/mgedmin/dotvim ~/.vim
If your vim is older than 7.3.1178, you'll also want to run :
~/.vim/install.sh
Then install all the plugins (this'll be an interactive) and compile C extensions for things like Command-T and YouCompleteMe :
make -C ~/.vim
Don't put any lines in your .vimrc that you don't understand.
Browse for ideas, copy interesting snippets. One by one.