A maior parte vem do link
1) Satisfaça as dependências antes de compilar o mono
wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
rpm -Uvh epel-release-6-8.noarch.rpm
yum install bison gettext glib2 freetype fontconfig libpng libpng-devel \
libX11 libX11-devel glib2-devel libgdi* libexif glibc-devel urw-fonts \
java unzip gcc gcc-c++ automake autoconf libtool make bzip2 wget
2) compile mono
cd ~
wget http://download.mono-project.com/sources/mono/mono-2.10.8.tar.gz
tar zxvf mono-2.10.8.tar.gz
cd mono-2.10.8
./configure --prefix=/usr/local
make
3) instale mono
make install